LTE Network & its applications in Indian Railways

LTE Network & its applications in Indian Railways

एलटीई नेटवर्क एवं भारतीय रेलवे में इसरे् अनुप्रयोग

अक्टूबर 2021

October 2021

CAMTECH/S/PROJ/2021-22/SP6

October 2021

केवल कार्ाालर्ीन उपर्ोग हेत ु For Official Use Only

भारत सरर्ार, रेल मंत्रालय GOVERNMENT OF INDIA, MINISTRY OF RAILWAYS

रे्मटेर्/एस /प्रोज/ 2021-22/एसपी6 CAMTECH/S/PROJ/2021-22/SP6

i

LTE Network & its applications in Indian Railways October 2021

Foreword

Several Railway organizations around the world are looking to migrate from the existing

communication technologies to the advanced ones in order to meet their current and future

requirements. A series of transformational initiatives have been contemplated by Indian

Railways to bring big upward shift in Railway operations, passenger safety & security and

enhancing passenger satisfaction.

With expansion of operations and advent of high-speed trains, the requirement from the

wireless communication infrastructure to support modern signalling system and data centric

applications like real time video surveillance and passenger information system, Remote

monitoring and diagnostics of rolling stock etc. has also been arisen in Indian railways.

Therefore, development of Ultra-high-speed wireless communication corridor along IR's

network has been identified as one of the facilitator for transformation of IR.

LTE (Long-Term Evolution) technology, the latest wireless Communication standard

worldwide, is one of the strong contender for meeting the present and future wireless

communication requirements of Indian Railways. Accordingly, IR has proposed to deploy

LTE based wireless corridor to facilitate Modern Railway Signalling and data centric

applications.

CAMTECH has prepared this handbook, which covers Introduction and Overview of LTE,

LTE technology, LTE System Architecture & Components and Design & Deployment of LTE

in Indian Railways.

I hope that this handbook will be useful to S&T engineers and maintenance staff of Indian

Railways to get them acquainted with the LTE technology, LTE Network & its applications in

Indian Railways.

I wish them all the success.

CAMTECH Gwalior Jitendra Singh

Principal Executive Director

ii


Preface

In Indian Railways, Intercommunication between Train Crew, Control office and Station

Master is critical for train operations and have stringent requirements for reliability,

availability, safety and security. Presently Mobile Train Radio communication (MTRC)

system, a digital wireless network based on GSM-R (Global System for Mobile

Communication-Railway) is being used to achieve this intercommunication. However, GSM

is a 2nd generation voice centric system with circuit switched technology and has hardly any

data handling capacity.

Long Term Evolution (LTE), also referred as 4G, is a fully packet-switched–based network

and is the latest mobile communication technology. With features like high data speed, Low

latency, Network reliability and Quality of Service, LTE is better suited for fulfilling the data

centric requirements and considering this, Indian Railways has decided to adopt and deploy

LTE across IR as next generation wireless communication technology.

CAMTECH has prepared this handbook with an objective to disseminate the information on

LTE technology, LTE Network & its applications in Indian Railways among S&T engineers

and maintenance staff of S&T department who deals with wireless communication.

This handbook covers Introduction and Overview of LTE, Future wireless communication

requirements of Indian Railways & FRMCS, GSM technology, LTE technology,

disadvantages of GSM and advantages of LTE over GSM, LTE System Architecture &

Components, Design, Deployment & Requirements of LTE in Indian Railways and other

important aspects. Figures and tables are also given for easy understanding of system

architecture and design.

We are sincerely thankful to AM (Telecom)/ Rly. Board, Telecom Directorate/ RDSO/

Lucknow, M/s Ericsson India Pvt. Ltd. And M/s Nokia Enterprises who have provided

valuable inputs for preparing this handbook. Since technological upgradation and learning is a

continuous process, you may feel the need for some addition/modification in this handbook. If

so, please give your comments on email address [email protected] or write to us at

CAMTECH, Indian Railways, In front of Adityaz Hotel, Airport Road, Maharajpur, Gwalior

(M.P.) 474005.

CAMTECH Gwalior Vijay Garg

Director (S&T)

mailto:[email protected]

iii


Table of Contents

Foreword ..................................................................................................................................... i

Preface ....................................................................................................................................... ii

Table of Contents ...................................................................................................................... iii

Abbreviations ........................................................................................................................... vii

List of Figures ........................................................................................................................... ix

List of Tables ............................................................................................................................. xi

Disclaimer ................................................................................................................................ xii

1 Chapter ............................................................................................................................... 1

Introduction and Overview of LTE ........................................................................................... 1

1.1 Introduction .......................................................................................................................... 1

1.2 Evolution of LTE .................................................................................................................. 2

1.3 Overview of LTE .................................................................................................................. 3

2 Chapter ............................................................................................................................... 4

Global System for Mobile Communication (GSM) ................................................................. 4

2.1 GSM - Overview ................................................................................................................... 4

2.2 GSM Network Architecture ................................................................................................. 4

2.2.1 Mobile Station (MS) ......................................................................................................................... 5

2.2.2 Base Station Subsystem (BSS) ......................................................................................................... 5

2.2.3 Network Switching Subsystem (NSS) .............................................................................................. 6

2.2.4 Operation Support Subsystem (OSS): .............................................................................................. 8

3 Chapter ............................................................................................................................... 9

Global System for Mobile Communication-Railway ................................................................ 9

(GSM-R) .................................................................................................................................... 9

3.1 Overview of GSM-R ............................................................................................................. 9

3.2 Special requirements of GSM-R Networks ........................................................................ 9

3.3 Features of GSM-R ............................................................................................................. 10

3.4 Applications of GSM-R ...................................................................................................... 10

3.5 GSM-R Network Architecture .......................................................................................... 10

3.5.1 Mobile Station (MS) ....................................................................................................................... 11

3.5.2 Cab radio ....................................................................................................................................... 12

3.5.3 Dispatcher ...................................................................................................................................... 12

3.6 Mobile Train Radio communication (MTRC) ................................................................. 12

iv


4 Chapter ............................................................................................................................. 13

Future wireless communication requirements of Indian Railways & FRMCS .................... 13

4.1 Next-generation wireless communication requirements of Indian Railways ................ 13

4.2 Future Railway Mobile Communication System (FRMCS) ........................................... 14

4.3 Railway Users of FRMCS .................................................................................................. 14

4.4 Requirements of FRMCS ................................................................................................... 15

4.5 Communication Requirements of IR through FRMCS .................................................. 15

4.5.1 Critical Communication Applications ............................................................................................ 16

4.5.2 Performance Communication Applications .................................................................................... 17

4.5.3 Business Communication Applications .......................................................................................... 18

4.5.4 Critical Support Applications ......................................................................................................... 18

4.5.5 Business Support Applications ....................................................................................................... 18

4.6 Shortcomings in the existing communication technologies ............................................. 18

4.7 Disadvantages of GSM/ GSM-R ........................................................................................ 18

4.8 Advantages of LTE/ LTE-R ............................................................................................... 20

5 Chapter ............................................................................................................................. 22

LTE technology ....................................................................................................................... 22

5.1 Introduction of LTE technology ........................................................................................ 22

5.1.1 LTE Frame Structure ...................................................................................................................... 23

5.1.2 Spatial Multiplexing ....................................................................................................................... 24

5.1.3 Transmit Diversity .......................................................................................................................... 24

5.1.4 Link Adaptation .............................................................................................................................. 25

5.1.5 Rate Matching ................................................................................................................................ 25

5.1.6 LTE deployment methodology ....................................................................................................... 25

6 Chapter ............................................................................................................................. 27

LTE System Architecture & Components .............................................................................. 27

6.1 Architecture of LTE System .............................................................................................. 27

6.2 Evolved Universal Terrestrial Radio Access Network (E-UTRAN) .............................. 27

6.3 Evolved NodeB (eNB) ......................................................................................................... 28

6.3.1 Antenna .......................................................................................................................................... 29

6.3.2 Remote Radio Head (RRH) ............................................................................................................ 30

6.3.3 Baseband Unit (BBU) .................................................................................................................... 31

6.4 Evolved Packet Core (EPC) ............................................................................................... 32

6.4.1 Mobility Management Entity (MME) ............................................................................................ 33

6.4.2 Home Subscriber Server (HSS) ...................................................................................................... 33

6.4.3 Serving Gateway (S-GW)............................................................................................................... 34

6.4.4 Packet Data Network Gateway (P-GW) ......................................................................................... 34

6.4.5 Policy and Charging Rules Function (PCRF) ................................................................................. 34

v


6.5 Interfaces in LTE ................................................................................................................ 35

6.6 Network Evolution towards LTE ...................................................................................... 35

7 Chapter ............................................................................................................................. 36

LTE-R and Implementation of LTE on Indian Railways ...................................................... 36

7.1 Introduction ........................................................................................................................ 36

7.2 LTE for Railways (LTE-R) ................................................................................................ 36

7.3 LTE System Architecture for Indian Railways ............................................................... 37

7.4 Applications of LTE in Indian railways ........................................................................... 38

7.5 Indian Railway Automatic Train Protection System (IRATP) ...................................... 39

7.6 Train Collision Avoidance System (TCAS) ...................................................................... 39

7.6.1 TCAS working over LTE ............................................................................................................... 40

7.7 Mission Critical Services (MCX) through LTE ............................................................... 41

7.7.1 Mission Critical Push to Talk (MCPTT) ........................................................................................ 42

7.7.2 Mission Critical Data (MCData) .................................................................................................... 43

7.7.3 Mission Critical Video (MCVideo) ................................................................................................ 43

7.7.4 Internet of Things (IoT) based Asset reliability monitoring ........................................................... 44

8 Chapter ............................................................................................................................. 45

Design, Deployment & Requirements of LTE in Indian Railways ....................................... 45

8.1 Radio Network Planning .................................................................................................... 45

8.2 General Requirements of LTE System for Indian Railways .......................................... 45

8.3 Specific Requirements of LTE System Architecture for Indian Railways .................... 46

8.4 Design, Deployment & Requirements of eNodeB ............................................................ 47

8.4.1 Cell Range and Inter eNodeB distance ........................................................................................... 47

8.4.2 Site Deployment Scenario of eNodeB (Schematic) ........................................................................ 48

8.4.3 Site Deployment Scenario of eNodeB (Actual Outdoor) .............................................................. 48

8.4.4 Simulations for deployment of eNodeB ......................................................................................... 49

8.4.5 Base Station Antenna Requirements .............................................................................................. 50

8.4.6 Tower Requirements ...................................................................................................................... 50

8.5 Design & deployment of Evolved Packet Core (EPC) ..................................................... 51

8.5.1 Requirements of EPC for deployment in IR ................................................................................... 52

9 Chapter ............................................................................................................................. 53

User Equipment (UE), On-board Equipment and Dispatcher System Design Requirements

53

9.1 Cab Radio System ............................................................................................................... 53

1. LTE Router/ Modem (Central Control Unit) .................................................................................. 53

2. Control Panel (MMI) & Display Unit ............................................................................................ 53

3. Rail Handset ................................................................................................................................... 53

vi


4. Rail Rooftop Antenna (To be mounted on the roof top of the drivers cabin) ................................. 54

5. Dual Redundant Power Supply ...................................................................................................... 54

9.1.1 Required features of Cab Radio System ......................................................................................... 54

9.1.2 Required features of Rail Rooftop Low profile Antenna ............................................................... 56

9.1.3 Required features of MCPTT Handset ........................................................................................... 57

9.2 Dispatcher System .............................................................................................................. 57

10 Chapter ............................................................................................................................. 58

Numbering Scheme for Mobile Communication Network (LTE) for Indian Railways ....... 58

10.1 General Numbering scheme of LTE Networks ................................................................ 58

10.1.1 International Mobile Subscriber Identity (IMSI) ............................................................................ 58

10.1.2 Mobile Subscriber International Subscriber Directory Number (MS ISDN) ................................. 59

11 Chapter ............................................................................................................................. 61

Quality of Service (QOS) Requirements of LTE in IR .......................................................... 61

11.1 LTE QoS Planning and Designing .................................................................................... 61

11.2 RAMS (Reliability, Availability, Maintainability and Safety) ........................................ 62

11.2.1 Preventive and Protective Solution Planning and Design ............................................................... 62

11.2.2 More Than 4 Nines Availability: .................................................................................................... 62

11.2.3 Geo Redundancy for Key Network Functions ................................................................................ 63

11.2.4 Redundancy in Radio Access Network: ......................................................................................... 64

References ................................................................................................................................ 65

CAMTECH Publications ......................................................................................................... 67

Our Objective ........................................................................................................................... 69

vii


Abbreviations

3GPP 3rd Generation partnership Project

ATC Automatic train control

ATO Automatic train operation

ATP Automatic Train Protection

AuC Authentication Center

BBU Baseband Unit

BSC Base Station Controller

BSS Base Station Subsystem

BTS Base Transceiver Station

CA Carrier Aggregation

CDMA Code division multiple access

CPRI Common Public Radio Interface

EDGE Enhanced Data Rates for GSM Evolution

EIR Equipment Identity Register

EIREN European Integrated Railway Radio Enhanced Network

eNB Evolved NodeB

EPC Evolved Packet Core

EPS Evolved Packet System

ERA European Union Agency for Railways

ETCS European Train Control System

ETSI European Telecommunications Standards Institute

E-UTRAN Evolved Universal Terrestrial Radio Access Network

FDD Frequency division duplex

FDMA Frequency division multiple access

FRMCS Future Rail Mobile Communications System

GBR Guaranteed Bit Rate

GPRS General Packet Radio Service

GSM Global System for Mobile Communications

GSM-R Global System for Mobile communication for Railways

HLR Home Location Register

HSR High Speed Railways

HSS Home Subscriber Server

IMSI International Mobile Subscriber Identity

IoT Internet of Things

IP Internet Protocol

LTE Long Term Evolution

LTE-R LTE for Railways

https://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolution

https://en.wikipedia.org/wiki/European_Telecommunications_Standards_Institute

viii


MCC Mobile country code

MCData Mission Critical Data

MCPTT Mission-Critical Push To Talk

MCVideo Mission Critical Video

MCX Mission Critical Services

MIMO Multiple Input Multiple Output

MME Mobility Management Entity

MNC Mobile network code

MTRC Mobile Train Radio Communication

MS Mobile Station

MSC Mobile Switching Center

MSIN Mobile subscription identification number

MS ISDN Mobile Subscriber International Subscriber Directory Number

NSS Network Switching Subsystem

OFDMA Orthogonal Frequency Division Multiple Access

OSS Operation Support Subsystem

QoS Quality of Service

PCEF Policy Control Enforcement Function

PCRF Policy and Charging Rules Function

P- GW Packet Data Network Gateway

RAMS Reliability, Availability, Maintainability and Safety

RAN Radio access network

RBC Radio block center

RRH Remote Radio Head

SC-FDMA Single Carrier - Frequency Division Multiple Access

S-GW Serving Gateway

TCAS Train Collision Avoidance System

TDD Time division duplex

TDMA Time division multiple access

UE User Equipment

UIC International Union of Railways

UMTS Universal Mobile Terrestrial System

VLR Visitor Location Register

VSS Video Surveillance System

WCDMA Wideband Code Division Multiple Access

https://en.wikipedia.org/wiki/Radio_access_network

ix


List of Figures

Figure 1.1: Circuit and packet domains ...................................................................................... 2

Figure 1.2: Network Solutions from GSM to LTE (Source: 3GPP.org) .................................... 3

Figure 2.1: GSM Network Architecture ..................................................................................... 4

Figure 3.1: GSM-R Architecture .............................................................................................. 11

Figure 3.2: NF Railway MTRC Network ................................................................................. 12

Figure 4.1: Grouping of FRMCS Applications ........................................................................ 16

Figure 5.1: OFDMA and SC-FDMA ....................................................................................... 22

Figure 5.2: Frequency-time domain representation of OFDM signal ...................................... 22

Figure 5.3: FDD & TDD .......................................................................................................... 23

Figure 5.4: Frame structure used for FDD ............................................................................... 24

Figure 5.5: LTE Peak User Bit Rates @ 05MHz BW .............................................................. 25

Figure 5.6: LTE Peak User Bit Rates @ 20MHz BW .............................................................. 26

Figure 6.1: LTE Architecture ................................................................................................... 27

Figure 6.2: E-UTRAN .............................................................................................................. 28

Figure 6.3: Equipment block diagram of eNB ......................................................................... 29

Figure 6.4: MIMO .................................................................................................................... 29

Figure 6.5: Typical structure of LTE omnicells ....................................................................... 30

Figure 6.6: Typical structure of LTE 3-sector cells (each cell includes 3 x 120 degree sectors)

.................................................................................................................................................. 30

Figure 6.7: Remote Radio Head ............................................................................................... 30

Figure 6.8: Baseband Unit ........................................................................................................ 31

Figure 6.9: eNB Antenna with RRH ........................................................................................ 31

Figure 6.10: eNB Antenna with RRH (Actual scenario) .......................................................... 32

Figure 6.11: EPC interfaces ...................................................................................................... 33

Figure 6.12: Evolution of LTE ................................................................................................. 35

Figure 7.1: LTE functional network architecture for Indian Railways .................................... 37

Figure 7.2: LTE System Architecture for Indian Railways ...................................................... 37

Figure 7.3: TCAS Call Flow over LTE – Loco approaches Station ........................................ 40

Figure 7.4: TCAS Call Flow over LTE – Loco Departure ....................................................... 40

Figure 7.5: TCAS Call Flow over LTE – Loco to Loco .......................................................... 40

Figure 7.6: TCAS Call Flow over LTE – SoS ......................................................................... 41

Figure 7.7: TCAS Call Flow over LTE – SoS – Station TCAS is Down ................................ 41

Figure 7.8: 3GPP releases on Mission Critical Services .......................................................... 42

Figure 8.1: eNodeB Antenna with RRH & BBU (Schematic) ................................................. 48

Figure 8.2: : eNodeB Antenna with RRH (Actual outdoor) ..................................................... 48

Figure 8.3: Typical LTE eNodeB deployment on Indian Railway Track ................................ 49

Figure 8.4: EPC Deployment/ Redundancy Diagram .............................................................. 51

Figure 10.1: Structure & Format of IMSI ................................................................................ 58

x


Figure 10.2: Number Structure of MSISDN ............................................................................ 59

Figure 10.3: IMSI for Indian Railways .................................................................................... 59

Figure 10.4: MS ISDN for Indian Railways ............................................................................. 60

xi


List of Tables

Table 6.1: LTE Network Interfaces .......................................................................................... 35

Table 8.1: Cell Range and Inter eNodeB distance ................................................................... 47

Table 8.2: Minimum no. of eNodeB locations ......................................................................... 47

Table 8.3: EPC Core traffic profile .......................................................................................... 52

Table 11.1: QOS Parameters for Indian Railway applications/ solutions on LTE ................... 61

xii


Disclaimer

It is clarified that the information given in this handbook does not

supersede any existing provisions laid down in the IR Telecom

Engineering Manual, Railway Board and RDSO publications. This

document is not statuary and instructions given are for the purpose

of learning only. The diagrams and figures given in the handbook

are indicative only. If at any point contradiction is observed, then

Signal Engineering Manual, Telecom Engineering Manual, Railway

Board/RDSO guidelines may be referred or prevalent Zonal

Railways instructions may be followed.

CAMTECH/S/PROJ/2021-22/SP6 1


1 Chapter

Introduction and Overview of LTE

1.1 Introduction

Communication technologies have always played a crucial role in Indian Railways. Operation

of this complex IR system requires reliable and timely information about the train movements

and the state of the infrastructure elements. Throughout the Indian Railways history, this

exchange of information has been provided by various communication technologies.

Capabilities and performance of the railway communication systems affect railway

operations. For instance, with faster information flow, train control/dispatching decisions can

be made faster. By increasing communication reliability, the probability of travel delays due

to communication failures is reduced. The more precise and detailed information available,

higher the safety that can be ensured.

Wireless communication is an important part of Indian Railways for operation and

maintenance of the rail networks ranging from Mobile Train Radio Communication (MTRC)

to those that facilitate entertainment to the Railway users. Global System for Mobile

Communications (GSM) is a worldwide standard for wireless mobile communication

developed by the European Telecommunications Standards Institute (ETSI). With GSM, ERA

(European Union Agency for Railways) and UIC (International Union of Railways), a global

organization for Railway, added extra functionality and called it GSM-R.

GSM-R (Global System for Mobile communication for Railways) has by far, one of the

most widely used digital wireless technologies to provide MTRC in IR. However, with the

advent of communication and internet revolution in various domains, Indian Railways also

cannot be far behind in bringing in new ways of leveraging advanced wireless technologies to

improve the Railway operations and to enhance the experience of Railway users. Though

GSM-R has very successfully been able to serve the needs of Railways for voice and

messaging needs, being a circuit switched technology, it has now outlived its utility due to

increasing data driven needs of Railways.

Several Railway organizations around the world are looking to migrate from the existing

technologies to the advanced ones in order to meet their current and future requirements. LTE

(Long-Term Evolution) is one of the strong contenders as a technology capable of meeting

the diverse requirements of Railways. LTE is a technology defined by 3GPP (3rd Generation

partnership Project), an international partnership project of major SDOs (Standards

Development Organizations) of the world, including Telecom Standards Development

Society, India (TSDSI) – the national SDO of India. LTE, which was initially designed for




regular Public Mobile Communications, is now being enhanced for various other domains

including Railways. UIC has set up Future Rail Mobile Communications System (FRMCS)

project to prepare the necessary steps towards the introduction of a successor of GSM-R. The

Future Railway Mobile Communication System - FRMCS has been prepared by UIC in order

to have a Mobile Train Communication System based on LTE termed as LTE-R.

1.2 Evolution of LTE

In GSM, the architecture relies on circuit-switching. This means that circuits are established

between the calling and called parties throughout the telecommunication network. In GSM, all

services are transported over circuit-switches telephony principally, but short messages (SMS)

and some data is also seen.

In GPRS, packet-switching (PS) is added to the circuit-switching. With this technology, data

is transported in packets without the establishment of dedicated circuits. This offers more

flexibility and efficiency. In GPRS, the circuits still transport voice and SMS (in most cases).

Therefore, the core network is composed of two domains: circuit and packet.

In UMTS (Universal Mobile Terrestrial System) (3G), this dual-domain concept is kept on the

core network side. To reach higher data rates in UMTS a new access technology WCDMA

(Wideband Code Division Multiple Access) was developed. The access network in UMTS

emulates a circuit switched connection for real time services and a packet switched connection

for datacom services. In UMTS the IP address is allocated to the UE (User Equipment) when

a datacom service is established and released when the service is released.

When designing the evolution of the 3G system, the 3GPP community decided to use IP

(Internet Protocol) as the key protocol to transport all services. This evolved Packet Switched

Domain system is termed as Evolved Packet System (EPS) or the LTE Network. EPS is an

end-to-end (E2E) all IP network. EPS is divided into two parts - LTE part, the access part and

the Evolved Packet Core (EPC) part, related to a core network. The main requirements for the

new access network were high spectral efficiency, high peak data rates, short round trip time

as well as flexibility in frequency and bandwidth. It was therefore, agreed that the EPC, which

is the Core network of EPS, would not have a circuit-switched domain anymore and that the

EPC should be an evolution of the packet-switched architecture used in GPRS/UMTS.

Figure 1.1: Circuit and packet domains



1.3 Overview of LTE

Long Term Evolution (LTE), also referred as 4G, is the latest family of mobile

communication standards developed by 3rd Generation Partnership Project (3GPP). The first

release of the LTE standard was published almost 20 years after the GSM standard. LTE is a

result of many developments and advances in telecommunications and electronics that

occurred during these years. Thus, from the telecommunications point of view, there are huge

differences between these two mobile technologies. All the evolution from GSM to LTE was

motivated by the needs of commercial mobile networks. The new solutions are optimized for

this type of networks. However, most of these enhancements are equally relevant to railway

mobile networks.

The main goal of LTE is to provide a high data rate, low latency and packet optimized radio

access technology supporting flexible bandwidth deployments. Same time its network

architecture has been designed with the goal to support packet-switched traffic with seamless

mobility and great quality of service.

Figure 1.2: Network Solutions from GSM to LTE (Source: 3GPP.org)



2 Chapter

Global System for Mobile Communication (GSM)

2.1 GSM - Overview

The Global System for Mobile Communications (GSM) is a standard developed by

the European Telecommunications Standards Institute (ETSI) to describe the protocols for

second-generation (2G) digital cellular networks used by mobile devices. It was first deployed

in Finland in December 1991.

2G networks developed as a replacement for first generation (1G) analog cellular networks.

The GSM standard originally described a digital, circuit-switched network optimized for full

duplex voice telephony. This expanded over time to include data communications, first

by circuit-switched transport, then by packet data transport via General Packet Radio

Service (GPRS), and Enhanced Data Rates for GSM Evolution (EDGE).

There are three main frequency bands used in GSM viz, GSM-900, GSM-1800 & GSM-1900

and three basic types of multiple access techniques:

Frequency division multiple access (FDMA)

Time division multiple access (TDMA)

Code division multiple access (CDMA)

2.2 GSM Network Architecture

Figure 2.1: GSM Network Architecture

https://en.wikipedia.org/wiki/The_Owl_House


https://en.wikipedia.org/wiki/2G

https://en.wikipedia.org/wiki/Cellular_network

https://en.wikipedia.org/wiki/Finland

https://en.wikipedia.org/wiki/1G

https://en.wikipedia.org/wiki/Duplex_(telecommunications)#Full_duplex

https://en.wikipedia.org/wiki/Duplex_(telecommunications)#Full_duplex

https://en.wikipedia.org/wiki/Telephony

https://en.wikipedia.org/wiki/Circuit_Switched_Data

https://en.wikipedia.org/wiki/Network_packet

https://en.wikipedia.org/wiki/General_Packet_Radio_Service

https://en.wikipedia.org/wiki/General_Packet_Radio_Service

https://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolution



The GSM network has the following sub-systems that work together to function as a whole:

❖ Mobile Station (MS)

❖ Base Station Subsystem (BSS)

❖ Network Switching Subsystem (NSS)

❖ Operation Support Subsystem (OSS)

2.2.1 Mobile Station (MS)

The mobile station (MS) is the starting point of a mobile wireless network. The MS can

contain the following components:

Mobile terminal (MT)—GSM cellular handset

Terminal equipment (TE)—PC or personal digital assistant (PDA)

The MS can be two interconnected physical devices (MT and TE) with a point-to-point

interface or a single device with both functions integrated.

2.2.2 Base Station Subsystem (BSS)

The BSS handles traffic and signalling between the MS or mobile phone and the NSS. The

BSS carries out transcoding of speech channels, allocation of radio channels to mobile

phones, paging, transmission and reception over the air interface and many other tasks related

to the radio network. A GSM network is comprised of many base station subsystems (BSSs),

each controlled by a BSC and a BSS can contain several BTSs.

BSS consists of two main components:

Base Transceiver Station (BTS)

Base Station Controller (BSC)

2.2.2.1 Base Transceiver Station (BTS):

When a subscriber uses the MS to make a call in the network, the MS transmits the call

request to the base transceiver station (BTS). The BTS is responsible for establishing the link

to the MS and for modulating and demodulating radio signals between the MS and the BTS.

The BTS contains the radio equipment (i.e., antennas, signal processing devices, and

amplifiers) necessary for radio transmission within a geographical area called a cell and the

equipment for encrypting and decrypting communications with the base station

controller (BSC). Typically a BTS will have several transceivers (TRXs) which allow it to

serve several different frequencies and different sectors of the cell.

In a large urban area, a large number of BTSs may be deployed.

https://en.wikipedia.org/wiki/Transcoding

https://en.wikipedia.org/wiki/Paging_(telecommunications)

https://en.wikipedia.org/wiki/Transmission_(telecommunications)

https://en.wikipedia.org/w/index.php?title=Reception_(telecommunications)&action=edit&redlink=1

https://en.wikipedia.org/wiki/Air_interface

https://en.wikipedia.org/wiki/Encryption

https://en.wikipedia.org/wiki/Base_station_subsystem#Base_station_controller

https://en.wikipedia.org/wiki/Base_station_subsystem#Base_station_controller

https://en.wikipedia.org/wiki/Frequency



2.2.2.2 Base Station Controller (BSC):

The base station controller (BSC) is the controlling component of the radio network, and it

manages the BTSs. Typically a BSC has tens or even hundreds of BTSs under its control. The

BSC reserves radio frequencies for communications and handles the handoff between BTSs

when an MS roams from one cell to another. The BSC is responsible for paging the MS for

incoming calls.

A key function of the BSC is to act as a concentrator where many different low capacity

connections to BTSs (with relatively low utilisation) become reduced to a smaller number of

connections towards the mobile switching center (MSC) (with a high level of utilisation).

Overall, this means that networks are often structured to have many BSCs distributed into

regions near their BTSs which are then connected to large centralised MSC sites.

BSC also provides all the required data to the operation support subsystem (OSS) as well as to

the performance measuring centers.

2.2.3 Network Switching Subsystem (NSS)

NSS is the core of the GSM system which performs the switching of calls between the mobile

and other fixed or mobile network users, as well as the management of mobile services such

as authentication. It is responsible for the handoff of calls from one BSS to another and

performs services such as charging, accounting, and roaming.

The NSS originally consisted of the circuit-switched core network, used for traditional GSM

services such as voice calls, SMS, and circuit switched data calls. It was extended with an

overlay architecture to provide packet-switched data services known as the GPRS core

network. This allows mobile phones to have access to services such as WAP, MMS and

the Internet.

NSS includes the following functional elements:

Mobile Switching Center (MSC)

Home Location Register (HLR)

Visitor Location Register (VLR)

Authentication Center (AuC)

Equipment Identity Register (EIR)

2.2.3.1 Mobile Switching Center (MSC):

The central component of the Network Subsystem is the MSC. The MSC performs the

switching of calls between the mobile and other fixed or mobile network users, as well as the

management of mobile services such as registration, authentication, location updating,

handovers, and call routing to a roaming subscriber. The MSC is a digital ISDN switch that

https://en.wikipedia.org/wiki/Concentrator

https://en.wikipedia.org/wiki/Network_Switching_Subsystem#Mobile_services_Switching_Centre_(MSC)

https://en.wikipedia.org/wiki/Core_network

https://en.wikipedia.org/wiki/GSM_services

https://en.wikipedia.org/wiki/GSM_services

https://en.wikipedia.org/wiki/Short_message_service

https://en.wikipedia.org/wiki/Circuit_Switched_Data

https://en.wikipedia.org/wiki/GPRS_core_network

https://en.wikipedia.org/wiki/GPRS_core_network

https://en.wikipedia.org/wiki/Wireless_Application_Protocol

https://en.wikipedia.org/wiki/Multimedia_Messaging_Service

https://en.wikipedia.org/wiki/Internet



sets up connections to other MSCs and to the BSCs. An MSC can connect to a large number

of BSCs.

2.2.3.2 Home Location Register (HLR):

The home location register (HLR) is the central database of all the subscribers registered to

the GSM network. The HLR stores both static data about subscribers, such as subscriber's

service profile, subscribed services, and a key for authenticating the subscriber and the

dynamic data such as current location.

It also contains information regarding real time location of the Roaming Subscriber, which is

passed to the MSC for routing incoming Calls to the Mobile Station. As soon as the Mobile

Station crosses a Cell boundary (also known as Location Area), this information is updated in

the HLR. Thus, HLR is the most important Database in the GSM structure.

2.2.3.3 Visitor Location Register (VLR):

The VLR is a database that contains temporary information about subscribers that is needed

by the MSC in order to service visiting (roaming) subscribers. The VLR is always integrated

with the MSC. When a Mobile Station (MS) roams into a new MSC area, the VLR connected

to that MSC will request data about the mobile station from the HLR and copy subscriber

information from the HLR to its local database. Later, if the mobile station makes a call, the

VLR will have the information needed for call setup without having to interrogate the HLR

each time.

Each main BTS in the network is served by exactly one VLR (one BTS may be served by

many MSCs in case of MSC in pool), hence a subscriber cannot be present in more than one

VLR at a time.

2.2.3.4 Authentication Center (AuC):

The Authentication Center is a protected database that stores a copy of the secret key stored in

each subscriber's SIM card, which is used for authentication. AUC authenticate each SIM

card that attempts to connect to the gsm core network (typically, when the phone is powered

on). Once the authentication is successful, the HLR is allowed to manage the SIM and

services described above.

AUC protects User Identity and allows a Secured Transmission.

2.2.3.5 Equipment Identity Register (EIR):

EIR is a database that stores the international mobile equipment identities (IMEIs) of all the

mobile stations in the network. The IMEI is an equipment identifier assigned by the

https://en.wikipedia.org/wiki/Base_Transceiver_Station

https://en.wikipedia.org/wiki/Base_transceiver_station

https://en.wikipedia.org/wiki/Authentication

https://en.wikipedia.org/wiki/SIM_card




manufacturer of the mobile station. An IMEI is marked as invalid if it has been reported stolen

or is not type approved.

The EIR provides security features such as blocking calls from handsets that have been stolen.

2.2.4 Operation Support Subsystem (OSS):

The OSS is the functional entity from which the network operator monitors and controls the

system.

The operations and maintenance center (OMC) is connected to all equipment in the switching

system and to the BSC. The implementation of OMC is called the operation and support

system (OSS).

Here are some of the OMC functions−

Administration and commercial operation (subscription, end terminals, charging, and

statistics)

Security Management

Network configuration, Operation, and Performance Management

Maintenance Tasks



3 Chapter

Global System for Mobile Communication-Railway

(GSM-R)

3.1 Overview of GSM-R

GSM for railways, a communication system for railway networks utilizing GSM technologies

and specific applications for railway operations.

Railways have some following specific requirements, which are not featured in GSM

Services:

♦ If some Emergency situation in the Locality makes all Channels busy due to sudden flood

of calls, and at that particular period, driver of a running train tries to originate a Call and

does not get Channel, a catastrophe might occur. Driver must have a facility to disconnect

some unimportant Subscriber and get the Channel on Priority. Thus, Priority cum Pre-

emption is an essential requirement.

♦ A situation may need that Track-side maintenance persons over 20 KMs area must get

same information without delay. A Commercial GSM system does not allow Group-cast

Mode Communication.

♦ In future, all the Train Controllers will have similar Numbering scheme. If the Mobile

Communications of different Zonal Railways are networked, a call from Driver will

disturb all Controllers. So, Location Dependent Addressing is also needed.

♦ Once, Cell phones are provided to all Drivers and the Driver of a particular train e.g.12137

is needed, it would be difficult for the Controller to remember the Cell phone number of

the Particular driver. It would be better, if there is Functional Addressing, which enables

dialing Code of Driver of 12137, which will be analyzed by the System and the specific

Driver at the Train will get the call.

These communication requirements were studied and identified by representatives of the

European railway operators and the communication standard, GSM-R was chosen by EIREN

(European Integrated Railway Radio Enhanced Network) to meet the railway requirements.

3.2 Special requirements of GSM-R Networks

♦ Efficient usage of a limited number of frequencies (20)

♦ 95 % Coverage for 95 % of the time in a designated coverage area with a level of above -

90 dBm



♦ Handover success rate of above 99.5 % even between GSM-R networks

♦ High availability of both transmission path and network equipment dependent on the

applications in use

♦ Coverage inside Tunnels, improved coverage in Railway stations and shunting Areas

3.3 Features of GSM-R

GSM-R is based on the cellular GSM technology, with further enhancements specific to

the requirements of Railways.

The Radio link uses both FDMA (Frequency Division Multiple Access) and TDMA (Time

Division multiple Access). The 900 MHz frequency bands for down link and up link

signal are 935-960 MHz and 890-915 MHz respectively.

In general, GSM-R uses characteristics that are identical or similar to those of the GSM

system, such as frequency spacing (200 kHz), modulation (Gaussian minimum shift

keying, GMSK) and access type (TDMA, TDD/FDD).

The general packet radio services (GPRS) for data communications up to 14.4 kbit/s is

supported by GSM-R for data transport in the same way as with the regular GSM system.

Two developments are taking place - one is LTE-R that is poised to replace GSM-R and

the other - UIC is formulating specifications for Future Radio Mobile Communication

System (FRMCS) as a successor or GSM-R.

3.4 Applications of GSM-R

The general applications of GSM-R are in the following fields:

Operational Voice Communication e.g. between Train Controller and Driver / Guard

of a Train, Driver to Guard of the same Train, Driver / Guard of a Train to Driver /

Guard of another Train, Emergency Communication, Track-side Communication,

Train Support Communication or Shunting Communication.

Local or Wide Area voice and Data Communication.

Signaling requirements as used in European Railway Train management System.

Passenger Communication

3.5 GSM-R Network Architecture

A typical GSM-R network is built of several cells alongside the track. Each cell is equipped

with one or more trans-receivers, depending upon the communication density. GSM-R

consists of following sub systems:

1. Mobile Station (MS)



2. Base Station Sub system (BSS)

3. Network and switching sub system (NSS)

4. Operating sub system (OSS)

5. Dispatcher

6. Cab Radio

The functionality of the above systems are same as described in GSM networks except some

ratings like RF powers of MS and BTS. There are different types of mobile equipment,

distinguished principally by their power and application. The fixed terminals are the ones

installed in driver’s cab. The RF output power is 8W, and handheld sets are of 2W power.

And the RF power of BTS will be 20-25 W.

3.5.1 Mobile Station (MS)

The Mobile station is classified into two categories.

1. The radios in the cabin of a locomotive - also known as cab radios - are installed

on board and are destined for the train conductors.

2. The mobile equipment are equal to the classical GSM's but give also access to all

functions that are developed for the digital radio network

There are three types of mobiles equipment:

♦ for general purposes (GPH),

♦ for operational purposes (OPH),

♦ for shunting (OPS)

Figure 3.1: GSM-R Architecture



3.5.2 Cab radio

Cab radio is the Radio equipment installed in the cabinet of the train driver. It provides

voice communications between trains and ground based organizations and personnel. The

equipment is compliant with EIRENE standards.

The key elements of the cab radio are:

1. The Cab Radio unit

2. The Drivers Control Panel OR Man machine Interface (MMI)

3. The Handset

4. The Loudspeaker

5. The GSM-R Antenna.

6. Power supply units

3.5.3 Dispatcher

Dispacher is responsible for the programming and traffic of the trains on the railway

network.

3.6 Mobile Train Radio communication (MTRC)

Indian Railways uses Mobile Train Radio communication (MTRC) system to facilitate inter-

communication between the train crew, Control office and Station Master. MTRC system is a

digital wireless network based on GSM-R (Global System for Mobile Communication-

Railway).

Figure 3.2: NF Railway MTRC Network



4 Chapter

Future wireless communication requirements of Indian

Railways & FRMCS

4.1 Next-generation wireless communication requirements of Indian Railways

The next-generation integrated wireless network for railway should achieve not only safe

operation of trains but also advanced railway services of the future. It should meet the general

requirements as under:

i) High-speed movement: The technology shall support high speeds of operations –

which can go up to 250 km/h or higher. Mobile voice and data communication shall be

provided for speeds low (<40kmph), normal (> 40kmph and < 250 kmph) and high

(>250 kmph) speeds.

ii) Transmission speeds: The future railway communication will include the video

transmission function (for real-time monitoring of passenger and/or coach status as well

as various railway customer services). The broadband wireless technology needs to

support transfer of large amount of data in real time. The rate of transfer can range from

low data transfer for control data to high data rates for video transmissions.

iii) Low latency: The latency requirement varies based on the application. In European

Train Control System (ETCS) Level 2, the maximum latency of end-to-end

communication for train control is specified as 500 msec. Shorter communication delay

time is required if we consider the increasing speed of trains in the future. In addition,

the voice call setup and connection should be performed in less than one second for an

emergency event.

iv) Network reliability and availability: The integrated wireless network for railway

should provide high network reliability and availability. The network reliability refers to

the reliable transmission of data information for the safety of railway operation and the

network availability indicates the percentage of time the network is fully functional and

operational.

v) Quality of Service (QoS): The latest wireless technologies support various QoS aspects

depending on different types of traffic and services. For example, certain types of

communications like train control signalling need to have higher priority over

information and lesser priority operational communications.

vi) Independent frequency and network: For the high reliability, availability, and safety

of the network, it is necessary to independently configure both wired and wireless

networks by separating from the commercial networks.



vii) Open standard: The technology needs to be based on open standards that will ensure

wider availability of products, guaranteed minimum functionality and performance and a

longer life of the technology. The technology can be as much aligned to global trends as

well in order to take advantage of the global scale of operations of railways.

4.2 Future Railway Mobile Communication System (FRMCS)

Future Railway Mobile Communication System (FRMCS) is the future worldwide

telecommunication system designed by International Union of Railways (UIC), in close

cooperation with the different stakeholders from the rail sector, as the successor of GSM-R

but also as a key enabler for rail transport digitalisation.

FRMCS is set to become the global standard for railway communications. This mobile

broadband-ready technology enables to improve safety and operational efficiency, support

innovative passenger services and accelerate digital transformation.

4.3 Railway Users of FRMCS

The following users are those identified to be users in IR and may not be necessarily

conclusive within FRMCS.

• Driver(s)

• Controller(s)

• Train staff:

o Train conductor(s)

o Catering staff

o Security staff

• Trackside staff:

o Trackside maintenance personnel

o Shunting team member(s)

• Railway staff (excl. all of above):

o Engine scheduler(s)

o RU operator(s)

o Catering scheduler(s)

o IM operator(s)

o Engineering personnel

• Station manager(s)

o Station personnel

o Depot personnel

o Etc.

• Member of the public:

o Passengers (on trains, on platforms, at stations, etc.)

o Other persons (on platforms, at level crossings, etc.)

• Systems:



o ATC on-board system

o ATO on-board system

o On-board system

o Ground system

o Trackside warning system

o Trackside system

o Sensors along trackside

o Trackside elements controlling entities (such as, for example, for level

crossings)

o Applications (such as, for example, those for monitoring lone workers, for

remote controlling of elements)

• Network operator

• Public emergency operator

4.4 Requirements of FRMCS

i) The FRMCS shall satisfy the communication needs of the railway operation.

ii) FRMCS shall support the applications independently of the used FRMCS networks and

radio access technologies by any of the users. Transition of a user to or from other

FRMCS networks or radio access technologies shall not lead to interruption of the

usage of the applications.

iii) The FRMCS shall place the human being at the centre of the design.

iv) The FRMCS shall support the application of the harmonised operational rules and

principles where available.

v) The FRMCS shall support the exchange of information and performance of actions

without the manual assistance of humans (machine-to-machine communication) both

for operational and maintenance purposes.

vi) The FRMCS shall mitigate the risk of miscommunication.

vii) The FRMCS shall be cost effective.

viii) The FRMCS shall provide precautionary measures to prevent unauthorized access.

4.5 Communication Requirements of IR through FRMCS

The communication requirement of LTE in IR shall be complying to FRMCS and can be

categorized as follows:

❖ Critical: applications that are essential for train movements and safety or a legal

obligation, such as emergency communications, shunting, presence, trackside

maintenance, ATC, etc.

❖ Performance: applications that help to improve the performance of the railway

operation, such as train departure, telemetry, etc.



❖ Business: applications that support the railway business operation in general, such as

wireless internet, etc.

4.5.1 Critical Communication Applications

4.5.1.1 Communications among trains, control centers and Stations

1. On-train outgoing voice communication from the driver towards the controller(s)

of the train

2. On-train incoming voice communication from the controller towards a driver

3. On-train outgoing voice communication from train staff towards a ground user

4. On-train incoming voice communication from a ground user towards train staff

5. Multi-train voice communication for drivers including ground user(s)

6. Banking voice communication (drivers of same train)

4.5.1.2 Communications for Maintenance and Shunting

1. Trackside maintenance voice communication

2. Shunting voice communication

3. Ground to ground voice communication

4. Data communication for Possession management

5. Trackside maintenance warning system communication

6. Shunting data communication

4.5.1.3 Communications for monitoring and control

1. Automatic train control communication

2. Automatic train operation communication

3. Remote control of engines communication

4. Monitoring and control of critical infrastructure.

Figure 4.1: Grouping of FRMCS Applications



5. Critical Real time video

4.5.1.4 Communications in Emergency situations

1. Railway emergency communication

2. On-train safety device to ground data communication

3. Public train emergency communication

4. Railway staff emergency communication

5. Public emergency call

6. Working alone

7. Critical Advisory Messaging services- safety related

4.5.1.5 Recording functions

1. Voice recording and access

2. Data recording and access

4.5.2 Performance Communication Applications

4.5.2.1 Communications among trains, control centers, stations and maintenance staff

1. Multi-train voice communication for drivers excluding ground user(s)

2. Record and Broadcast

3. Real time video call

4.5.2.2 Communications within the train

1. On-train voice communication

2. Lineside telephony

3. On-train voice communication towards passengers (public address)

4. Station public address

5. Communication at stations and depots

4.5.2.3 Data Communications for Telemetry, monitoring and Information sharing

1. On-train telemetry communications

2. Infrastructure telemetry communications

3. On-train remote equipment control

4. Monitoring and control of non-critical infrastructure

5. Driver advisory - train performance

6. Transfer of CCTV archives

4.5.2.4 Data Communications for net connectivity

1. Wireless on-train data communication for train staff

2. Wireless data communication for railway staff on platforms



3. Train departure related communications

4. Messaging services

4.5.3 Business Communication Applications

1. Information help point for public

2. Emergency help point for public

3. Wireless internet on-train for passengers

4. Wireless internet for passengers on platforms

4.5.4 Critical Support Applications

1. Assured Voice Communication

2. Multi user talker control

3. Role management and presence

4. Location services

5. Authorisation of communication

6. Authorisation of application

7. Safety application key management communication

8. Assured data communication

9. Inviting-a-user messaging

10. Arbitration

4.5.5 Business Support Applications

1. Billing information

4.6 Shortcomings in the existing communication technologies

The shortcomings of the VHF based units led to the development and use of GSM-R as the

first digital train communication system widely deployed across the globe. GSM-R also

happens to the only Mobile Train Radio communication system (MTRC) on Indian Railways.

As communication demands increased and the capabilities of electronic devices evolved, it

has become necessary to support data communication as much as voice communication and

GSM being a circuit switched technology, has now outlived its utility and rapidly becoming

obsolete due to increasing data driven needs of Railways.

4.7 Disadvantages of GSM/ GSM-R

GSM does not provide packet-switched transmission. Therefore, data communication

must be delivered by Circuit-Switched Data (CSD), which cannot assign the network

resources based on the actual demand. This means that data is transmitted over virtual

circuits, just like voice frames. Being bursty in nature, data sources send varying amounts

of data at irregular intervals. Such a bursty transmission does not fit well into a fixed



circuit provided by GSM. As a result, circuits are often underutilized and network

resources are wasted.

GSM-R resources are assigned symmetrically in uplink and downlink. However, data-

based services often generate different amount of traffic in the two directions. Hence,

symmetry of GSM-R connections means that either uplink or downlink is overbooked and

the network resources are wasted further.

Transmission latency in GSM-R network is estimated to be in the range between 200 ms

and 400 ms. If the low bitrate is added to that, the GSM-R delay performance turns out to

be very poor. Thus, GSM - R may not fulfil requirements of delay-sensitive applications.

GSM-R Call setup time is in the range of about 5 s. GSM-R requirements state that the

setup procedure cannot exceed 8.5 s (95% of cases) and 10 s (100% of cases). This may be

sufficient for a voice call, but such a long connection setup time is unacceptable for many

real- time applications.

Capacity of GSM-R networks is insufficient. a GSM-R cell can only accommodate as

many trains as many traffic channels (time-slots) it has available. A typical cell offers 23

traffic channels. Since each train occupies one channel, such a typical cell can

accommodate at most 23 ETCS equipped trains. However, in practice, some of the traffic

channels must be kept for voice communication, as well as for handover procedures.

Therefore, a typical GSM-R cell can accommodate less than 20 trains. It has been widely

recognized that GSM-R capacity is insufficient, especially in areas with high density of

train traffic.

There is no end-to-end encryption of user data.

The 4 MHz bandwidth of GSM-R can support 19 channels of 200 KHz width. This is

sufficient for voice communication, as voice calls are limited in time and do not occupy

resources continuously. However, the current capacity turns out to be insufficient for the

next-generation railway system, where each train needs to establish a continuous data

connection with a radio block center (RBC) and each RBC connection needs to constantly

occupy one time slot.

As a narrowband system, GSM-R cannot provide advanced services and adapt to new

requirements. The maximum transmission rate of GSM-R per connection is 9.6 kb/s,

which is sufficient only for applications with low demands; message delay is in the range

of 400 ms, which is too high to support any real-time application and emergency

communication.

GSM-R is becoming an obsolete technology. Commercially networks have moved away

from GSM due to limitations of GSM technology. Many countries have started shutting

down 2G networks. This also will have an impact on the equipment available in the



market and the support provided for installations. Since Industry has given commitment to

support the GSM-R technology only until 2030, the life of such systems can be affected.

Due to the above limitations, GSM-R must eventually evolve or to be replaced by some

advanced communication technology in Railways.

4.8 Advantages of LTE/ LTE-R

Long-term evolution (LTE)-R, which is based on the LTE standard, is a likely candidate to

replace GSM-R in the future for the following reasons:

Data as well as voice can be exchanged between participants. As a fully packet-switched–

based network, LTE is better suited for data communications.

Compared with GSM-R, LTE network assigns the network resources to users and

applications depending on the actual transmission demand.

LTE offers a more efficient network architecture and thus has a reduced packet delay,

which is one of the crucial requirements for providing ETCS messages.

LTE introduces a simplified core network called Evolved Packet Core (EPC) with fewer

elements than in the legacy standards. The circuit-switched part of the backbone, which

was used in earlier network generations for voice transmission, has been abandoned in

favour of a fully packet-switched solution.

Modulation and coding schemes are dynamically chosen in LTE based on the radio

conditions and the traffic demand. This link adaptation mechanism allows the network to

balance between throughput and reliability of the radio transmission.

The new radio interface offers much higher spectral efficiency than any other legacy

mobile communication standard. This is due to the advanced modulation (OFDMA),

multiplexing (up to 64QAM) as well as usage of Multiple Input Multiple Output (MIMO).

MIMO is a technique where multiple antennas are used at both the transmitter and the

receiver to increase the link reliability and the spectral efficiency.

LTE can operate in different bandwidths: 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz or

20 MHz (and more with carrier aggregation in LTE-Advanced). This range of bandwidths

allows network operators to flexibly manage their available radio spectrum. For instance,

an operator may split the radio band used by the GSM network (spectrum re-farming).

One part would still be used by GSM, while in the other part a new LTE network may be

deployed. As the number of terminals equipped with LTE radio increase over time, the

bandwidth of the LTE network could be increased accordingly. Therefore, the migration

to LTE can be gradual and spread over years.

LTE offers QoS mechanisms providing traffic differentiation, protection and prioritization

over both radio and backbone networks.



LTE provides standardized mechanisms for inter-working with all legacy 3GPP

technologies. Mechanisms, such as cell re-selection, handover and connection release,

allow mobile terminals to quickly and seamlessly transfer from one radio network to

another. Due to this, it may be possible to have interoperability between the new and old

systems at least to some extent.

LTE is the latest family of mobile communication standards. Hence, it has much lower

obsolescence risk than any of the previous standards.

Considering the advantages listed above, LTE is gaining a considerable interest from the

railway community, industry and suppliers, as one of the most likely candidate for

replacement of GSM-R.



5 Chapter

LTE technology

5.1 Introduction of LTE technology

LTE is based on orthogonal frequency division multiplexing (OFDM) thus enabling it to

transmit efficiently over higher bandwidths while being resilient to the channel conditions and

interference. In the downlink, i.e. from base station to the user equipment, LTE uses OFDMA

(Orthogonal Frequency Division Multiple Access) and in the uplink, i.e. from user equipment

to the base station, it uses SC-FDMA (Single Carrier - Frequency Division Multiple Access).

The SC-FDMA is adopted for uplink due to its low peak-to-average power ratio (PAPR) when

compared to OFDMA. This enables a better coverage in the uplink by utilizing the power

amplifier efficiently.

The OFDM splits the wideband carrier in to multiple overlapping narrowband orthogonal

subcarriers for carrying the data. A frequency-time domain representation of a 5 MHz OFDM

signal is shown in the below Figure 5.2: Frequency-time domain representation of OFDM

signal.

Figure 5.2: Frequency-time domain representation of OFDM signal

Figure 5.1: OFDMA and SC-FDMA



OFDMA technology has been incorporated into LTE because it enables high data bandwidths

to be transmitted efficiently while still providing a high degree of resilience to reflections and

interference.

LTE was initially designed to support a scalable bandwidth (BW) of up to 20 MHz with a

peak data rate of 300 Mbps using a 4 × 4 multiple input multiple output (MIMO)

configuration and 64 QAM modulation, and later extended to support up to 100 MHz by

aggregating five 20 MHz carriers. A unified frame and symbol structure is defined for all the

supported bandwidths with the same subcarrier spacing of 15 KHz.

5.1.1 LTE Frame Structure

LTE uses OFDM as its waveform, and defines two types of frame structures for frequency

division duplex (FDD) and time division duplex (TDD) mode.

The radio frame length is of 10 ms duration, and it is divided into 10 subframes each of 1 ms

duration. Each subframe consists of two slots each of length 0.5 ms. Each slot contains 7 (for

normal CP) or 6 (for extended CP) OFDM symbols. The unit of allocation is in terms of

resource blocks (RB) which composed of one slot duration and 12 subcarriers. Scheduling is

done in terms of RB pairs. A resource element (RE) is the smallest element in the RB which is

of one subcarrier for one OFDM symbol duration. Therefore, a RB consists of 84 REs (for

normal CP), or 72 REs (for extended CP).

Figure 5.3: FDD & TDD



It is to be noted that not all subcarriers are used for transmission. For example, dc subcarrier

and the subcarriers at the edges are left as guard band. There are 100 RBs in a 20 MHz BW.

5.1.2 Spatial Multiplexing

Spatial multiplexing (SM) allows transmitting different data streams on the same time and

frequency resource by exploiting the spatial dimension of the radio channel. When this is

performed to increase the spectral efficiency by exploiting the multiple antennas at the

eNodeB and a single user, it is called as single user MIMO (SU-MIMO). When the multiple

antennas at the eNodeB and the multiple antennas located across users located in different

geographical location are exploited to increase the overall system throughput, it is called as

multiuser MIMO (MU-MIMO).

5.1.3 Transmit Diversity

Transmit Diversity schemes play a key role in ensuring reliable communication in fading

scenarios. It helps to improve the robustness of the data transmission by sending replicas over

multiple transmit antennas. An antenna specific code w.r.t. channel is applied on the signal

Figure 5.4: Frame structure used for FDD



before transmission to achieve the diversity gain at the receiver. Appropriate MIMO modes

are chosen based on the user velocity, channel signal to interference plus noise ratio (SINR),

and user equipment (UE) capability.

5.1.4 Link Adaptation

Link Adaptation is a technique used by the eNodeB to select appropriate modulation and

coding rate based on the channel quality information feedback by the UE to maximize the

throughput. The UE computes the post processing SINR of the receiver, and map to

appropriate MCS supported by LTE and the index is reported back to the eNodeB.

5.1.5 Rate Matching

The data transmitted to the UE in LTE are in terms of transport blocks (TBs). The TB size in

LTE is of pre-determined lengths, and moreover, the allocation of resources is in terms of

multiples of RB pairs. The chosen TB size may not match the size of the allocated resources.

To fit the TB in the allocated resources, some of the bits will be punctured, or more redundant

bits are added depending on the bits in the TB and the number of bits the allocated resources

can accommodate. Puncturing and repetition will result in increasing and decreasing the code

rate, respectively.

5.1.6 LTE deployment methodology

Figure 5.5: LTE Peak User Bit Rates @ 05MHz BW



Figure 5.6: LTE Peak User Bit Rates @ 20MHz BW



6 Chapter

LTE System Architecture & Components

6.1 Architecture of LTE System

The LTE network called EPS is divided into two parts - LTE part which deals with the

technology related to a radio access network Evolved Universal Terrestrial Radio Access

Network (E-UTRAN) and Evolved Packet Core (EPC) part which deals with the technology

related to a core network.

User Equipment (UE) is connected to the EPC over E-UTRAN (LTE access network). The

Evolved NodeB (eNodeB) is the base station for LTE radio. The EPC is composed of five

network elements: the Serving Gateway (Serving GW), the PDN Gateway (PDN GW), the

MME, PCRF and the HSS (Figure 6.1: LTE Architecture).

6.2 Evolved Universal Terrestrial Radio Access Network (E-UTRAN)

E-UTRAN or LTE is the access part of the Evolved Packet System (EPS). E-UTRAN is a

radio access network (RAN) of base stations called evolved NodeB (eNB) through which the

user equipment (UE) are linked to the LTE core network. There is no centralized intelligent

controller, and the eNBs are normally inter-connected via the X2-interface and towards the

core network by the S1-interface. The reason for distributing the intelligence amongst the

base-stations in LTE is to speed up the connection set-up and reduce the time required for a

handover.

Figure 6.1: LTE Architecture

https://en.wikipedia.org/wiki/Radio_access_network



It provides higher data rates, lower latency and is optimized for packet data. It

uses OFDMA radio-access for the downlink and SC-FDMA on the uplink.

6.3 Evolved NodeB (eNB)

The Evolved NodeB (eNodeB) is the base station for LTE radio. eNodeB is the RAN (Radio

Access Network) node in the network architecture that is responsible for radio transmission to

and reception from UEs ( User Equipment) in one or more cells.

The radio coverage area of an eNodeB is called a cell. Accordingly, the cell site is where the

eNodeB radio equipment and its antennas are placed.

The eNodeB is connected to EPC nodes by means of an S1 interface. The eNodeB is also

connected to its neighbor eNodeBs by means of the X2 interface. eNB is equivalent of BSS in

GSM-R.

Physically the eNodeB consists of the followings:

● Antenna

● Remote Radio Head (RRH)

● Baseband Unit (BBU)

Figure 6.2: E-UTRAN

https://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiple_access

https://en.wikipedia.org/wiki/SC-FDMA



6.3.1 Antenna

LTE adopts multiple input multiple output (MIMO) as the antenna technology. MIMO is a

technique where multiple antennas are used at both the transmitter and the receiver to increase

the link reliability and the spectral efficiency. One of the main problems that previous

telecommunications systems have encountered is that of multiple signals arising from the

many reflections that are encountered in antenna deployments. By using MIMO, these

additional signal paths can be used to advantage and are able to be used to increase the

throughput.

Based on the antenna type, there can be two types of cell deployments: omnidirectional cell

and sectorized cell. The omnidirectional cell also called omnicell, includes an Omni antenna

to cover the signals in 360-degree field which practically means in all directions.

In contrast to omnicells, the sectorized cells have been designed to enhance the cellular

system capacity. The sectorization refers to when cells are divided into different parts called

sector. The antenna for eNodeB is replaced with sector antenna owning different order of

sectorization, e.g. three, six, or nine with 120, 60, 40 degrees' coverage, respectively, where

each sector is covered by one of the sector antennas. The importance of cell sectorization is

mainly due to improving the transmission capabilities and capacity gain and thereby, it is

widely used by mobile communication industries to increase the data rate.

Figure 6.4: MIMO

Figure 6.3: Equipment block diagram of eNB

eNB Cabinet eNB Tower

Antenna

RRH

RF Cable

CPRI (Common Public

Radio Interface)

BBU

Router

OFC

EPC



6.3.2 Remote Radio Head (RRH)

An RRH transmits and receives wireless signals. An RRH

converts the digital baseband signals from BBU that have

been subjected to protocol-specific processing into radio

frequency (RF) signals and power-amplifies them to

transmit to UE. The RF signals received from UE are

amplified and converted to digital baseband signals for

transmission to the BBU.

Figure 6.5: Typical structure of LTE omnicells

Figure 6.6: Typical structure of LTE 3-sector cells (each cell includes 3 x 120 degree sectors)

Figure 6.7: Remote Radio Head



6.3.3 Baseband Unit (BBU)

The BBU is responsible for digital baseband signal processing, termination of S1 line used for

connecting with a core network, termination of X2 line used for connecting with the

neighboring eNodeB, call processing and monitoring control processing. IP packets received

from the core network are modulated into digital baseband signals and transmitted to the

RRH(s). The digital baseband signals received from the RRH(s) are demodulated and IP

packets are transmitted to the core network.

The interfacing between BBU and RRH is with Optic Fibre Cable and compliant to the

Common Public Radio Interface (CPRI) specification or OBSAI (Open Base Station

Architecture Initiative).

The BBU and RRH shall be designed to work in 5 MHz (paired) in 700 MHz band (703-748

MHz Uplink & 758-803 MHz Downlink) allocated to Indian Railways. The eNodeB (BBU

and RRH) shall support Omni Cell and Cell Sectorization (Sectoring) and MIMO

configuration as per site requirement.

Figure 6.9: eNB Antenna with RRH

Figure 6.8: Baseband Unit

RRH

Antenna



6.4 Evolved Packet Core (EPC)

The Evolved packet Core (EPC) is the Core network of LTE system. It is a framework for

providing converged voice and data on a LTE network. 2G and 3G network architectures

process and switch voice and data through two separate sub-domains: circuit-switched (CS)

for voice and packet-switched (PS) for data. Evolved Packet Core unifies voice and data on an

Internet Protocol (IP ) service architecture and voice is treated as just another IP application.

This allows operators to deploy and operate one packet network for 2G, 3G, and LTE.

EPC is composed of four network elements: Mobility Management Entity (MME), Home

Subscriber Server (HSS), Serving Gateway (S-GW) and Packet Data Network Gateway (P-

GW).

Figure 6.10: eNB Antenna with RRH (Actual scenario)

https://searchmobilecomputing.techtarget.com/definition/Long-Term-Evolution-LTE

https://searchnetworking.techtarget.com/definition/3G-third-generation-of-mobile-telephony

https://searchnetworking.techtarget.com/definition/circuit-switched

https://searchunifiedcommunications.techtarget.com/definition/Internet-Protocol



6.4.1 Mobility Management Entity (MME)

The MME is the key control-node for the LTE access-network. It handles the signalling

related to mobility and security for E-UTRAN access. It is involved in the bearer

activation/deactivation process and is also responsible for choosing the Serving Gateway for a

UE at the initial attach and at time of intra-LTE handover. It manages session states and is

responsible for authenticating the user (by interacting with the Home Subscriber Server). It is

responsible for the tracking and the paging of UE in idle-mode. It is the termination point of

the Non-Access Stratum (NAS) signaling and is responsible for generation and allocation of

temporary identities to UEs. The MME also provides the control plane function for mobility

between LTE and 2G/3G access networks with the S3 interface and terminates the S6a

interface towards the HSS for roaming UEs.

6.4.2 Home Subscriber Server (HSS)

The HSS (for Home Subscriber Server) is a database that contains user-related and subscriber-

related information. It also provides support functions in mobility management, call and

session setup, user authentication and access authorization.

A Home Network may contain one or several HSSs: it depends on the number of mobile

subscribers, on the capacity of the equipment and on the organisation of the network.

Figure 6.11: EPC interfaces

https://en.wikipedia.org/wiki/Home_Subscriber_Server



6.4.3 Serving Gateway (S-GW)

The gateways (Serving GW and Packet Data Network GW) deal with the user plane. They

transport the IP data traffic between the User Equipment (UE) and the external networks. The

Serving GW is the point of interconnect between the radio-side and the EPC. As its name

indicates, this gateway serves the UE by routing the incoming and outgoing IP packets. For

each UE associated with the EPS, at a given point of time, there is a single Serving GW. For

idle state User Equipment, the Serving Gateway terminates the downlink data path and

triggers paging when downlink data arrives for the User Equipment.

It is the anchor point for the intra-LTE mobility (i.e. in case of handover between eNodeBs)

and between LTE and other 3GPP accesses. It is logically connected to the other gateway, the

PDN GW.

6.4.4 Packet Data Network Gateway (P-GW)

The PDN GW acts as the interface between the LTE network and the external IP networks. It

manages quality of service (QoS). The PDN GW routes packets to and from the PDNs. The

PDN GW performs policy enforcement, packet filtering for each user, charging

support, lawful interception and packet screening. Another key role of the PDN GW is to act

as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX

and 3GPP2.

3GPP specifies these gateways independently but in practice they may be combined in a

single "box" by network vendors. A piece of User Equipment (UE) may have simultaneous

connectivity with more than one Packet Data Network Gateway for accessing multiple packet

data networks. If a UE is accessing multiple PDNs, there may be more than one PDN GW for

that UE.

The PDN GW and the Serving GW may be implemented in one physical node or separated

physical nodes.

6.4.5 Policy and Charging Rules Function (PCRF)

The Policy and Charging Rules Function (PCRF), is a combination of the Charging Rules

Function (CRF) and the Policy Decision Function (PDF). PCRF brings together and enhances

capabilities from earlier 3GPP releases to deliver dynamic control of policy and charging on a

per subscriber and per IP flow basis. It is responsible for policy control decision-making, as

well as for controlling the flow-based charging functionalities in the Policy Control

Enforcement Function (PCEF), which resides in the P-GW. The PCRF provides the QoS

(Quality of Service) authorization that decides how a certain data flow will be treated in the

PCEF and ensures that this is in accordance with the user’s subscription profile.

In a nutshell, PCRF is the policy manager of the LTE technology. All the quality of service

(QoS) rules and regulations are distributed to the PDN GW by the PCRF.

https://searchunifiedcommunications.techtarget.com/definition/QoS-Quality-of-Service

https://en.wikipedia.org/wiki/Lawful_interception

https://en.wikipedia.org/wiki/3GPP2



6.5 Interfaces in LTE

Interface represents a channel on which two network entities exchange information. Interfaces

are needed in LTE to deliver information (signaling or user data) for a subscriber or network

element. The various network interfaces are defined by 3GPP. All network vendors or

manufacturers are required to comply with these standards.

Table 6.1: LTE Network Interfaces

Interface Name Connecting Nodes

LTE-Uu UE & eNB

S1-U eNB & S-GW

S1-MME eNB & MME

X2 eNB & eNB

S11 MME & S-GW

S5/ S8 S-GW & P-GW

S7 P-GW & PCRF

S10 MME & MME

S6a MME & HSS

6.6 Network Evolution towards LTE

Figure 6.12: Evolution of LTE



7 Chapter

LTE-R and Implementation of LTE on Indian Railways

7.1 Introduction

Railway specific network parameters depend both on the technology and the implementation

aspects. The performance of LTE-R will be better than GSM-R in terms of several attributes

like data rates, spectral efficiency, Handover success rates and Mobility which affect the

railway network specific performance. The coverage of LTE technology is better than the

existing cellular and GSM-R, with support for higher throughput at longer distances.

7.2 LTE for Railways (LTE-R)

With the advent of High Speed Railways (HSR), a new communication system for Railways

is required to handle increasing traffic, ensure passenger safety, and provide real-time

multimedia information. It is thus relevant for Railways to replace the current GSM-railway

(GSM-R) technology with the next-generation railway-dedicated communication system

providing improved capacity and capability.

The International Union of Railways, UIC a global organization for Railway set up a project

in 2014 to prepare the necessary steps towards the introduction of a successor of GSM-R.

Subsequently, the Future Railway Mobile Communication System (FRMCS) was prepared by

UIC in order to have a Mobile Train Communication System based on LTE since LTE has a

simple flat architecture, high data rate, and low latency, making it an acceptable choice to be

the next generation of HSR wireless communication.

LTE for Railways (LTE-R) is a next-gen communications network dedicated for railway

services, enabling high-speed wireless voice and data communications inside trains, from the

train to the ground and from train to train. LTE-R can also support passenger information

applications, CCTV, traffic management, ticketing and other services on a single network.

The LTE-R systems are compatible with modern train automation systems like European

Train Control System (ETCS) or similar and also interoperable with other legacy mobile

communication systems such as GSM and UMTS.



7.3 LTE System Architecture for Indian Railways

LTE for Railways consists of User Equipment, Evolved Universal Terrestrial Radio Access

Network, Evolved Packet Core and Session Initiation Protocol (SIP) with MCX capabilities

for Mission-Critical Push To Talk (MCPTT), Mission Critical Data (MCData) and Mission

Critical Video (MCVideo) application, other voice communications can be through IP using

SIP clients.

Figure 7.1: LTE functional network architecture for Indian Railways

Figure 7.2: LTE System Architecture for Indian Railways



7.4 Applications of LTE in Indian railways

Installing an Ultra-high-speed LTE based communication corridor along IR network would

cater to the current and future data and voice needs for Train-Ground and Train-Train

communication for improved train operations, passenger safety and passenger security

services and remote rail asset monitoring & management.

The applications of LTE for Railways, the next generation Mobile Train Radio

Communication System, can be classified under the following three broad categories:

1. Passenger Safety & Service:

Advanced Signalling systems like European Train Control System (ETCS) Level

2/Train Collision Avoidance System (TCAS).

Emergency communications from train to control, train to stations and between train-

to-train, etc.

Increased carrying capacity (throughput) Advanced signaling systems allow more

trains to run across a given point or segment of the track which effectively increase the

carrying capacity (throughput) of the same fixed civil and electrical infrastructure

2. Video Surveillance System:

Live surveillance camera feeds from trains will ensure security of passengers coupled with

video analytics, this can help in prevention and detection of crime, not only in Indian

Railways network but also outside in the peripheral areas.

3. Internal improved Railway management:

Staff communication system.

Remote monitoring of Railways asset to improve their availability

The following main applications/solutions are to be implemented on LTE in Indian

Railways:-

1. Indian Railway Automatic Train Protection System (IRATP) through Train Collision

Avoidance System (TCAS) or any other similar systems as specified by Indian Railways

2. Mission Critical Services (MCX) as per FRMCS standards

3. Video Surveillance System in locomotives for Level Crossing Gate/ Tunnels/ Bridges

4. Onboard Passenger Information System (PIS) consisting of passenger information display

and passenger announcement system

5. Internet of Things (IoT) based Asset reliability monitoring

6. Onboard Video Surveillance System (VSS) for Passenger Security

7. Broadband Internet on Running Train (Onboard Wi-Fi facility through LTE).



5 MHz (paired) Spectrum in 700 MHz band (703-748 MHz Uplink & 758-803 MHz

Downlink, also specified as Band 28 in 3GPP/ETSI standards) has been allocated to

Indian Railways for implementing above services.

7.5 Indian Railway Automatic Train Protection System (IRATP)

Automatic Train Protection (ATP) is a type of train protection system which continually

checks that the speed of a train is compatible with the permitted speed allowed by signalling,

including automatic stop at certain signal aspects. If it is not, ATP activates an emergency

brake to stop the train. In other words it provides Fail safe protection against over speed,

collision & other hazardous conditions through train detection, train separation &

interlocking. The main functions of ATP are:

Detection and Prevention of SPAD (Signal passed at Danger)

Display of signal aspect, movement authority, target distance and speed

Continuous train control

Protection for Permanent and temporary speed restriction

7.6 Train Collision Avoidance System (TCAS)

Train Collision Avoidance System (TCAS) is an indigenously developed Automatic Train

Protection (ATP) System meant to provide protection to trains against Signal Passing at

Danger (SPAD), excessive speed and collisions.

TCAS provides continuous update of Movement Authority (distance up to which the train is

permitted to travel without danger). Hence, during unsafe situations when brake application is

necessitated, and the Crew has either failed to do so, or is not in position to do so, automatic

brake application shall take place.

TCAS has additional features to display information like speed, location, distance to signal

ahead, Signal aspects etc. in Loco Pilot’s cab and generation of Auto and Manual SOS

messages (Distress messages) from Loco as well as Station unit in case of emergency

situation.

The communication between Stationary TCAS and Loco TCAS units shall be Safety Integrity

Level -4 (SIL-4) certified, while Loco TCAS to Loco TCAS communication, Non-Signalling

based additional collision protection features (i.e. Head-on, Rear end & Side Collision) and

Manual SoS are non-SIL (not failsafe).

At present UHF Radio communication technique is being used for communication in

TCAS which is to be upgraded to LTE.



7.6.1 TCAS working over LTE

Figure 7.3: TCAS Call Flow over LTE – Loco approaches Station

Figure 7.4: TCAS Call Flow over LTE – Loco Departure

Figure 7.5: TCAS Call Flow over LTE – Loco to Loco



7.7 Mission Critical Services (MCX) through LTE

The LTE system in IR shall provide the necessary services, software and associated hardware

to support Mission Critical Services (MCX) as per FRMCS standards. MCX Solution

provides voice, data and video capabilities to the LTE system by using LTE terminals and are

based on SIP Core.

Mission Critical Services includes:

Mission Critical Push to Talk (MCPTT)

Mission Critical Data (MCData)

Mission Critical Video (MCVideo)

Figure 7.6: TCAS Call Flow over LTE – SoS

Figure 7.7: TCAS Call Flow over LTE – SoS – Station TCAS is Down



7.7.1 Mission Critical Push to Talk (MCPTT)

MCPTT, the standard developed by 3GPP, is a push-to-talk functionality that “meets the

requirements of public safety mission-critical voice communication, which include high

availability/reliability, low latency, support for group calls and [one-to-one] calls, talker

identification, device-to-device direct communications, emergency calling, clear audio

quality, etc.

MCPTT is now typically used to refer to 3GPP’s “Mission-Critical Push-to-Talk over LTE”

standard, which is part of 3GPP Release 13, which was finalized in March 2016.

According to 3GPP, Release 14 included enhancements to MCPTT as well as other mission-

critical services over LTE, such as video and mobile data.

7.7.1.1 Overview of MCPTT

A Push To Talk service provides an arbitrated method by which two or more users may

engage in communication. Users may request permission to transmit (e.g., traditionally by

means of a press of a button). The Mission Critical Push To Talk (MCPTT) service supports

an enhanced PTT service, suitable for mission critical scenarios, based upon 3GPP system

services. The requirements for Mission Critical Push To Talk (MCPTT) service defined

within can also form the basis for a non-mission critical Push To Talk (PTT) service.

The MCPTT Service is intended to support communication between several users (a group

call), where each user has the ability to gain access to the permission to talk in an arbitrated

manner. However, the MCPTT Service also supports Private Calls between pairs of users.

Figure 7.8: 3GPP releases on Mission Critical Services

http://www.3gpp.org/NEWS-EVENTS/3GPP-NEWS/1875-MC_SERVICES



Though the MCPTT Service primarily focuses on the use of the 3GPP system there might be

users who access the MCPTT Service through non-3GPP access technology, dispatchers and

administrators are examples of this. Dispatchers and administrators are special users who have

particular admin and call management privileges which normal users might not have. In

MCPTT dispatchers can use an MCPTT UE (i.e., 3GPP) or a non-3GPP access connection to

the MCPTT Service based on a "dispatcher and Administrator" interface. Through this

interface a user is able to access and manage the services related to on the network and those

common to on the network and off the network.

7.7.2 Mission Critical Data (MCData)

MCData defines a service for Mission Critical Data services. As well as voice services,

current mission critical users have been increasing their use of data services, including low

throughput services on legacy networks and data services on commercial networks. This need

will continue to grow with the creation of the new multimedia services. The MCData service

needs to provide a means to manage all data connections of mission critical users in the field

and provide relevant resources to the ones who need it. The migration to LTE networks will

allow mission critical users to operate current and new data services whilst relying on the

fundamental capabilities of mission critical communication such as defined for MCPTT.

The MCData Service will reuse functions including end-to-end encryption, key management,

authentication of the sender, etc. in order to provide group communications for data services.

As for all mission critical services, users affiliate to groups in order to receive

communications directed to the group.

In addition, the MCData Service will provide a set of generic capabilities such as: messaging,

file distribution, data streaming, IP proxy, etc. The MCData Service will also provide specific

services such as conversation management, data base enquiries, internet access, robots

control.

7.7.3 Mission Critical Video (MCVideo)

MCVideo defines a service for Mission Critical video communication using LTE transport

networks. MCVideo service includes:

Video capture and encoding of the video information

Secure streaming and storing of the video information

Video decoding and rendering of the video information

Processing of the video information, including the ability to annotate video frames and

recognize video features

Mission critical and public safety level functionality (e.g. group sessions, affiliations,

end-to-end confidentiality, emergency type communications) and performance (e.g.

low latency)



Transmission and control of the parameters relevant to those functions

Secure operation such that video information can be reasonably un-impeachable when

used in evidentiary procedures

Definition and configuration of MCVideo groups and applications

Configuration of the MCVideo users' profiles and of the MCVideo UEs

Interoperability with other services and systems.

7.7.4 Internet of Things (IoT) based Asset reliability monitoring

LTE-R provides the railway IoT services, such as real-time query and tracking of trains and

goods. It helps to enhance transport efficiency and extend service ranges.

IoT can also be used to improve train safety. Most of today’s trains rely on trackside switches

located in remote areas.

With the IoT and remote monitoring, it is possible to remake trackside infrastructure from

switches to power lines, which could automate many of the routine safety checks and reduce

the costs of maintenance.



8 Chapter

Design, Deployment & Requirements of LTE in Indian

Railways

8.1 Radio Network Planning

Radio network Planning needs to follow process of simulating the predicted coverage and data

rates from a given number of sites (eNB) based on certain inputs like traffic, technology,

product and required services through an intelligent Simulation tool. The simulation tool runs

its algorithm basis the critical inputs provided, intended area, clutter spread, elevation

variation, Transmitted/Received power and propagations losses.

Actual cell range needs to be calculated using planning tool where, clutter morphologies (like

River, vegetation and other clutter losses are considered).

8.2 General Requirements of LTE System for Indian Railways

The Long Term Evolution (LTE) Technology Solution (Hardware and Software) for

Mobile Train Communication System of Indian Railways shall be compliant to

3GPP/ETSI LTE Release 16 or later Specification with emphasis on features supporting

mission critical application like public safety/ Railways.

The LTE systems shall be interoperable with other legacy Railway mobile communication

systems such as GSM-R for voice communication in Indian Railways except with

equipment declared as End of life on a global basis.

Proposed EPS solution/nodes must be upgradable to support future LTE release with

additional HW and SW functionality needed without necessitating any change to existing

LTE solution.

The LTE shall be compatible and suitable bearer network for ETCS and Indian Railway

Automatic Train Protection System i.e. Train Collision Avoidance System (TCAS). The

related application software, interface protocols between LTE and Stationary TCAS &

Loco TCAS ATP systems shall be vendor (both LTE and TCAS vendors) agnostic.

The system shall be designed to work in 700 MHz spectrum (703-748 MHz Uplink &

758-803 MHz Downlink, 3GPP/ETSI Band 28) with 5 MHz (paired) Carrier bandwidth

allocated to Indian Railways.

LTE shall be able to support Frequency Division Duplex (FDD). The system shall support

different carrier bandwidth (Size) starting with 5 MHz up to 20 MHz as per 3GPP



specification. The system shall also support Carrier Aggregation (CA) as per 3GPP/ETSI

specification.

The LTE shall be suitable for Indian Railway Train speeds from 0 - 250 Kmph which

should be upgradable to higher train speeds up to 350 Kmph.

The 230 V/ 50 Hz AC nominal Electrical Power Supply available in Indian Railway

premises with suitable stabilisation shall be provided for LTE.

The LTE systems including EPC, eNodeB and other equipment provided by different

OEM‟s shall be interoperable and shall be seamlessly integrated with each other in such a

way that all the features and services are available in the solution.

The LTE Radio Network shall be planned with double radio coverage (100% Coverage

Overlap) where in case of one eNodeB failure, the adjacent eNodeBs will cover the

requirements.

Special solutions need to be designed and considered for areas such as Train tunnels,

Bridges, Ghat sections and Mountainous curves etc.

8.3 Specific Requirements of LTE System Architecture for Indian Railways

The System shall support for V2V (Vehicle-to-Vehicle) services based on LTE side link

and LTE- based V2X (vehicle-to-everything) Services.

MCX and dispatcher should be a completely integrated solution and support to define

MCX aliases for functional addressing and location based addressing.

The E-UTRAN shall provide coverage and capacity for the MCX application as well as

general UE connectivity in the following areas:

The above ground area within the Indian Railway’s limit of Train Control Authority to

a distance of 50 meters from the nearest running rail in all the directions. The entirety

of all rail tunnels, yards and stations, above or below ground.

All above and underground areas utilised operationally or during an emergency by the

Indian Railways, train cabs, emergency exit risers, tunnels, cross passages, the E-UTRAN

shall provide coverage and capacity for the TCAS/ETCS application in the following

areas:

All rail within the Indian Railways limit of Train Control authority to a distance of 5

meters from the nearest running rail in all directions.

The MCX Application Server OEM should provide their MCX Client which shall be

designed based on Mission Critical requirements of Railways.



8.4 Design, Deployment & Requirements of eNodeB

8.4.1 Cell Range and Inter eNodeB distance

The approximate Cell Range and Inter eNodeB distance for desired throughput are as below:

Table 8.1: Cell Range and Inter eNodeB distance

Rural Suburban Urban

UP link Cell Edge

Throughput (Kbps)

590 970 1075

DN Link Cell Edge Throughput (Kbps) 2030 2890 3475

Approximate Cell Range Radius (Km) 5.95 4.58 2.85

Approximate Inter eNodeB Distance with

Double Coverage (100% Coverage

Overlap) (Km)

5.95 4.58 2.85

The minimum no. of eNodeB shall be provided as per below:

Table 8.2: Minimum no. of eNodeB locations

Clutter Type Minimum No. of eNodeB Locations

per 100 route Km

Rural 15

Sub Urban 20

Urban 33



8.4.2 Site Deployment Scenario of eNodeB (Schematic)

8.4.3 Site Deployment Scenario of eNodeB (Actual Outdoor)

Figure 8.1: eNodeB Antenna with RRH & BBU (Schematic)

Figure 8.2: : eNodeB Antenna with RRH (Actual outdoor)



8.4.4 Simulations for deployment of eNodeB

The deployment planned for conducting the performance evaluation through simulations is as

shown in Figure 8.3: Typical LTE eNodeB deployment on Indian Railway Track. The

eNodeBs are deployed at a height of 25 meters along both sides of the railway track

alternatively in a planned manner to cover a range of 4 to 7 kms. A two sectors per site

deployment with narrow antenna beam pattern to cover both sides of the tracks is considered.

The number of antennas and its gain at the BS will depend on desired link budget to cover the

track and throughput requirement. Users will be dropped uniformly along the track for a width

of 3 meters, which is the maximum carriage width found in Indian railways and with height of

2.5 meter to cover ground to middle berth height for a maximum carriage height of 4 meters

found in Indian railways.

Figure 8.3: Typical LTE eNodeB deployment on Indian Railway Track



8.4.5 Base Station Antenna Requirements

The Antenna shall work in 700 MHz spectrum (703-748 MHz Uplink & 758- 803 MHz

Downlink, 3GPP/ETSI Band 28) with 5 MHz (paired) Carrier bandwidth allocated to

Indian Railways.

The Antennas to be used for Railway tracks shall be of directional type. Indian Railways

may have one Sector at Terminal stations and usually two Sectors for single route

sections in either direction of the Base Station (eNodeB). There may be three or more

Sectors in case for additional spur route in the junction station/line.

LTE Antennas shall be installed with 2x2 MIMO techniques. The BBU (Baseband Unit)

and RRH (Remote Radio Head) shall be hardware ready to support 2x2 MIMO and no.

of Sectors as per site requirement.

8.4.6 Tower Requirements

The LTE Towers shall be ground based Towers, self-supporting type of heights 25, 30,

35 and 40 meters or as per site requirement.

The Towers shall preferably be of following types:-

i) 4 legged Angular Steel Tower

ii) 3 legged Tubular Steel Tower

iii) Hybrid of Angular and Tubular Steel Tower

iv) Monopole Steel Tower

Each Towers, Angular/ Tubular/ Monopole shall be designed specific to site/location

requirements. The Monopole Towers shall preferably be used where there is a footprint

restriction or any other reasons as per site condition.

The Tower shall be designed considering no. of Antennas & Equipment/ accessories,

their physical dimensions and various other required factors. The Tower design/drawing

shall clearly mention no. of antennas & equipment and their mounting locations on the

Tower.

The Tower structure as per site requirement if any may have provision of equipment

platform at suitable height, Working/ Rest Platform, access ladders and cable ladders

etc. The fence and gate may be provided between tower legs.

The Tower design shall be approved by agencies such as Bureau of Indian Standards

(BIS), Telecom Engineering Centre (TEC), Structural Engineering Research Centre

(SERC), Central Power Research Institute (CPRI) and Indian Railway/ RDSO or any

other competent agencies/ institutions/ authorities as specified by the purchaser.



Roof Top Towers of suitable design and height shall also be used as per site

requirement.

The Tower manufacturer/ Supplier shall be ISO 9001:2015 approved and have Tower

design and demonstration capabilities and quality assurance process for manufacturing.

8.5 Design & deployment of Evolved Packet Core (EPC)

Initially, LTE shall be implemented on Indian Railways with two EPCs at two different

geographic locations (Northern and Southern). Later on, two more EPCs (Western and

Eastern) may be provided based on increase of traffic capacity. The EPCs shall be redundant

and virtualized.

The Northern EPC (at Delhi) and Southern EPC (at Secunderabad) shall work in redundant

mode with 1:1 redundancy. The Northern/Southern EPC should be planned to work on full

capacity of designated Zonal Railways. The same capacity shall be kept as redundant in

Southern/Northern EPC. At each location EPC shall support local redundancy on

Server/port/connectivity level.

MME, HSS & PCRF components of Evolved packet core can be centralized and shall be geo-

redundant. Application servers shall also be centralized and situated along with the core.

In order to reduce the latency over the transport network Serving Gateway (S- GW) and

Packet Data Network Gateway (P-GW) may be deployed at all Zonal Railway locations.

Figure 8.4: EPC Deployment/ Redundancy Diagram



Table 8.3: EPC Core traffic profile

EPC Traffic

Parameter

Unit Centralized Core

components Qty.

(Main Core Site)

Centralized Core

Components Qty. (Geo-

Redundant site)

S-GW and P-

GW at each

zone

Total number Nos. 4,00,000 4,00,000 5555

of subscribers

Total

Throughput Gbps 50 50 5

8.5.1 Requirements of EPC for deployment in IR

EPC shall support high availability and geo-redundancy with uptime of 99.999%.

It should be expandable to cater higher capacities as per the Railways future network

requirements.

EPC shall be interoperable with any LTE-RAN vendor and vice versa.



9 Chapter

User Equipment (UE), On-board Equipment and

Dispatcher System Design Requirements

The UE category for Indian Railways shall be selected based on the spectrum bandwidth and

UL/DL data throughput requirement.

9.1 Cab Radio System

The Cab Radio System includes the following sub systems:-

1. LTE Router/ Modem (Central Control Unit)

2. Control Panel (MMI) & Display Unit

3. Rail Handset



4. Rail Rooftop Antenna (To be mounted on the roof top of the drivers cabin)

5. Dual Redundant Power Supply

9.1.1 Required features of Cab Radio System

Each Train Engine (Loco) shall be provided with 2 nos. of Cab Radio Systems in

redundant mode for Indian Railways front and Rear Loco compartments. The Cab Radio

System shall provide Voice and Data communication for train operational requirements.

The Cab Radio System shall support latest 3GPP/ETSI 4G and 5G LTE spectrums and

bandwidths. It shall work on the spectrum assigned for LTE to Indian Railways. Cab

Radio System shall support Mission Critical application as per latest 3GPP/ETSI 4G and

5G release 16 or later specifications.

The Cab Radio System shall meet TCAS/ETCS standard requirements as per relevant

specifications for train operation and automation system for Indian Railways.

The Cab Radio System shall meet requirements of FRMCS/EIRENE specification. The

Cab Radio shall have the following minimum functions/features:-

A. Driver call related functions:

i) Call controller

ii) Call other drivers in the area

iii) Send railway emergency call

iv) Confirm receipt of railway emergency calls

v) Communicate with other drivers on the same train

vi) Call train staff

vii) Call other authorized users

viii) Receive incoming voice calls

ix) Terminate calls

x) Receive text messages

xi) Enter/leave shunting mode

xii) Monitor calls to other on train users/devices

xiii) Forward calls/cancel call forwarding to/from driver hand held



B. Other driver related functions:

i) Powering up radio

ii) Switch radio MMI on and off

iii) Select language

iv) Adjust loud speaker volume

v) Select mobile radio network

vi) Register and deregister train number

vii) Register and deregister on train users

viii) Register and deregister stock numbers

ix) Store/retrieve numbers and their details

x) Invoke supplementary services

xi) Invoke tests

C. Other cab radio functions:

i) Automatic connection of incoming calls to appropriate on-train users

or devices (conductor, public address system, data systems, etc.).

ii) Automatic establishment of outgoing calls initiated by on-train users

or devices.

iii) Automatic handling of calls of varying priorities.

iv) Send to the controller(s) a signal on activation of driver safety

device.

v) Transmit Railway emergency call event indication to “train-borne

recorder”.

vi) Run-time diagnostics

One Cab Radio System shall consist of at least two Mobile network terminations, in

active/ standby configuration i.e. comprising of minimum two mobile equipment and

SIM cards.

The SIM cards shall be physically integrated with the cab radio set and shall not be able

to be removed except by maintenance staff.

The Control Panel shall consist of capacitive touch screen display unit of day light

readable type for displaying information. Control panel shall have dedicated hard buttons

configurable for specific functions.

Cab Radio System shall receive remote software upgrades via a ground-based

management terminal. Cab Radio System shall also support software updates via USB

Stick. There shall be provision for retrieving system logs from USB/Ethernet ports.



The Speakers in the Driver Cab shall be loud enough to be audible in the running Train.

The radio should be able to provide five levels of adjustment (numbered 1 to 5) for each

volume range setting.

Separate Rail Rooftop Low Profile Antenna shall be provided for each Cab Radio

System.

The Cab Radio System shall be connected to TCAS/ ETCS systems with suitable

interfaces through LTE Router/ Modem equipment. The Cab Radio System shall also be

connected to other on-train systems application through LTE Router/ Modem equipment.

The following interfaces for the on-train systems application may be provided:-

1. TCAS/ ETCS

2. Train borne recorder

3. Public Address interface

4. Intercom and other interfaces as required

The various equipment in the Cab and their redundant equipment shall be connected over

Optical Fibre Media or any other media of industry standard in Ring Arrangement.

The various systems/sub systems in the Cab Radio System for voice and data shall be

connected with suitable cables and wires complying to relevant specifications and

standards for Rolling Stock Application.

The Ethernet interface between Cab Radio and client application shall be on industrial

grade fibre or CAT6 cable with suitable M12/M23 connectors.

An emergency power supply should be provided for Cab Radio System which will enable

the driver’s radio to continue to operate for a period of at least 2 hour in the event of

failure of the train’s main power supply.

All design manufacturing, testing and installation of Cab Radio equipment shall comply

with the quality procedures defined in ISO 9001.

9.1.2 Required features of Rail Rooftop Low profile Antenna

LTE Cab Radio Rail Rooftop Low profile Antenna shall cover LTE spectrums and

bandwidths. It shall work on the spectrum assigned for LTE to Indian Railways.

The mechanical dimension shall be such that it meets mounting requirements on the Rail

Rooftop of Indian Railways for electrified and non-electrified sections, Sub-urban

sections, bridges, tunnels etc.



The antenna shall be Omni directional with minimum 6 dBi gain and support minimum 2

x 2 MIMO antenna configuration.

9.1.3 Required features of MCPTT Handset

The MCPTT Handsets shall support latest 3GPP/ETSI LTE spectrums and frequency

bands. It shall work on the spectrum assigned for LTE to Indian Railways.

MCPTT Handsets shall also support the GSM-900 MHz network of Indian Railways.

It shall support Mission Critical application as per latest 3GPP/ETSI release 16 or later

specifications and support Carrier Aggregation (CA).

9.2 Dispatcher System

Dispatcher is an MCPTT User who participates in MCPTT communications for command and

control purposes.

The Dispatching System should be able to provide a flexible, reliable and comfortable

solution enabling efficient and effective voice and text-message communication and

communication management in various PMR communication technologies such as LTE and

PBX network environment. It should be used in:-

dispatching centers for the controlling and handling of entire fleets of subscribers

centers of effective alarm and control functions

emergency center for handling specific, public and other emergent events

other management and operational centers

Dispatching System shall use IP based interface to connect to the communication

network infrastructures for voice communications. It should support IP-based architecture

and packet- switch-based message routing strategy.

Dispatcher System should run on commercial off-the-shelf (COTS) hardware.

Dispatcher System should be built on a client / server architecture.

Dispatcher should be developed on top of a multi-technology and multi-vendor platform.



10 Chapter

Numbering Scheme for Mobile Communication Network

(LTE) for Indian Railways

10.1 General Numbering scheme of LTE Networks

All mobile users in the LTE network must be assigned a certain addresses or identities in

order to identify, authenticate and localize them. The following numbers and identities are

assigned for administration of each mobile station in the network.

10.1.1 International Mobile Subscriber Identity (IMSI)

The IMSI is a number that uniquely identifies every user of a cellular network. It is also used

for acquiring other details of the mobile in the home location register (HLR) or as locally

copied in the visitor location register.

The IMSI is a string of decimal digits, up to a maximum length of 15 digits, which identifies a

unique subscription. The IMSI consists of three fields: the mobile country code (MCC), the

mobile network code (MNC), and the mobile subscription identification number (MSIN).

Mobile country code (MCC)

The MCC is the first field of the IMSI and is three digits in length and identifies a country.

Mobile network code (MNC)

The MNC is the second field of the IMSI, it is two or three digits in length and is administered

by the respective national numbering plan administrator.

Mobile subscription identification number (MSIN)

The MSIN is the third field of the IMSI, it is up to 10 digits in length, and is administered by

the relevant MNC assignee to identify individual subscriptions.

Figure 10.1: Structure & Format of IMSI

https://en.wikipedia.org/wiki/Cellular_network

https://en.wikipedia.org/wiki/Home_location_register

https://en.wikipedia.org/wiki/Visitor_location_register



10.1.2 Mobile Subscriber International Subscriber Directory Number (MS ISDN)

Mobile Station/Subscriber International Subscriber Directory Number (MSISDN) is a number

(Mobile Phone Number) used to identify a mobile phone number internationally.

It is the mapping of the telephone number to the subscriber identity module in a mobile or

cellular phone.

The MSISDN composition follows the international ISDN numbering plan with the following

structure:

Country Code (CC), up to three digits;

National Destination Code (NDC), typically two or three digits;

Subscriber Number (SN), a maximum of 10 digits.

RDSO has approved and issued Uniform Numbering Scheme for Mobile Communication

Network (GSM-R) for Indian Railways. The same scheme shall be applicable for LTE.

The IMSI and MSISDN for Indian Railway shall be as below:

Figure 10.2: Number Structure of MSISDN

Figure 10.3: IMSI for Indian Railways




Figure 10.4: MS ISDN for Indian Railways



11 Chapter

Quality of Service (QOS) Requirements of LTE in IR

As railways will be running a number of rail applications on the same LTE network it is

important to plan and derive an e2e QoS design, taking the Railways key applications, use

cases, and call scenarios into account and ensure;

End to end LTE QoS design techniques

End to End product support for QoS

11.1 LTE QoS Planning and Designing

MCX , Train control (ETCS) and Platform information will run on the same network. From

QoS design perspective, priority should be planned to support the vital applications and hence

train control and MCX must be given higher priority. Some rail applications are delay

sensitive but do not demand high DL and/or UL throughput.

The one-to-one mapping of standardized QCI values to standardized characteristics for the

tentative services shall be as under:

Table 11.1: QOS Parameters for Indian Railway applications/ solutions on LTE

QC

I

Priorit

y Level

Packet

Delay

Budge

t

Packe

t

Error

Loss

Rate

Example Services Mapping of Indian Railway

applications (Tentative)

Resource Type: GBR (Guaranteed Bit Rate)

1 2 100 ms 10-2 Conversational Voice Voice Mobile Communication

2 4 150 ms 10-3 Conversational

Video (Live Streaming)

Live Video Streaming from

Accident Site (ART) or similar

3 3 50 ms 10-3 Real Time Gaming Not Applicable

4 5 300 ms 10-6 Non-Conversational

Video (Buffered

Streaming)

Live Video Streaming

from Accident Site (ART)

65 0.7 75 ms 10-2 Mission Critical user

plane Push To Talk

voice (e.g., MCPTT)

Mission Critical Services

66 2 100 ms 10-2 Non-Mission- Critical

user plane

Push To Talk voice

Voice Mobile Communication



Resource Type: Non GBR

5 1 100 ms 10-6 IMS Signalling Train Automation and

Protection Services i.e. TCAS,

ETCS and other services

6 6 300 ms 10-6 Video (Buffered

Streaming) TCP- based

(e.g., www, e-mail, chat,

ftp, p2p file sharing,

progressive video etc.)

Video Surveillance System

(CCTV), Passenger Information

System and Real Time Train

Information System, IoT

Services etc.

7 7 100 ms 10-3 Voice, Video (Live

Streaming)

Interactive Gaming

Voice Mobile Communication,

Live Video Streaming from

Accident Site (ART) & Video

Surveillance System (CCTV)

69 0.5 60 ms 10-6 Mission Critical delay

sensitive signalling (e.g.,

MC-PTT signalling)

Mission Critical Services

11.2 RAMS (Reliability, Availability, Maintainability and Safety)

System design and architecture of LTE network for Railways, not only mandates additional

technical capabilities but also requires careful planning and designing considerations, which

go beyond to normal Mobile operator network design.

Design for Mission critical applications requires:

Very high reliability and availability (More than four 9s)

Well defined corridor (railways track, platform and depots) coverage

Guaranteed latency, packet loss with strict tolerance levels

Low to medium throughput applications

Quality of Service (E.g. Priority and Pre-emption)

Security

11.2.1 Preventive and Protective Solution Planning and Design

As stated above the LTE solutions for Rail require careful requirement analysis and solution

planning/design to comply with Indian Railways RAMS requirements. The planning and

design of the technical solution must not only take the reliability and availability into account

but must also consider the system maintainability and safety requirements throughout the

system life cycle.

11.2.2 More Than 4 Nines Availability:

Availability of rail systems are usually expected to be ≥ 99.99%. A system availability target

of 99.995% or 99.999% are often required by rail operators for new mission critical radio



communication systems. Further, it is expected that any system deployed for mission critical

rail applications, must avoid any single point of failures.

From solution design perspective this means the end to end LTE network must

adhere to minimal unplanned outages, avoiding any single point of failures. (E.g. 26.283

minutes in a year for 99.995.

For train control, ETCS systems alone must adhere to 99.99% availability. When LTE is

being used as the DCN (Data Communication Network) subsystem in the ETCS, this

means that LTE network must be planned and designed to support more than 99.99%

availability.

11.2.3 Geo Redundancy for Key Network Functions

Rail operators usually request physical location (geo) redundancy for the key network

functions (Redundancy at minimum two geographically separated locations). This

requirement is influenced by two key reasons;

i) To ensure system availability of key technical nodes or key functional failures

ii) To maintain minimum operational capacity in the rail network in an unlikely event of

a disaster. (natural or man-made, e.g. floods, earth quakes, terrorist attacks at a

primary site)

When designing redundancy into a network, it is important to visualize the network as an end

to end interdependent system. It is crucial to evaluate and understand the impact when one

subsystem becomes unavailable or has degraded performance. If a particular sub system in the

network affects the desired performance of the system as a whole, an appropriate redundancy

mechanism should be planned and incorporated.

It is expected that a LTE network running mission critical applications (e.g. automatic train

control, MCX) will have the following key nodes in different physical (geo) locations to

provide redundancy.

LTE core (User Data Centre (UDC), Evolved Packet Core (EPC), Service Aware

Policy Control (SAPC) and associated routers and switches)

OSS

MCX-PTT Application Server

IP-Transport core aggregation nodes (as part of the IP-transport and LTE backhaul

redundancy architecture)



11.2.4 Redundancy in Radio Access Network:

When an LTE network is used for MCX and automatic train control, (ETCS) redundancy in

the radio access network and train on-board equipment are also mandatory.

Planning for sufficient redundancy in the e2e network, including radio access network is

important to maintain the availability and reliability targets of a rail network. From solutions

perspective, appropriate redundancy in RAN should be planned and designed taking all of the

following interdependent areas in to account:-

Track-side coverage deployment models

eNodeB configuration models

On-board coverage system models

Train on-board equipment (Cab radio equipment, On-board LTE devices)

IP-Transport and LTE backhaul solution and architecture

LTE core network solution and architecture

Applications



References

1. IR Telecom Manual 2021

2. RDSO Technical Advisory Note (TAN) Document No. STT/TAN/LTE/2021,

Version 1.0

3. “Requirements of Wireless Communications in Indian Railways” – Project

Report on “LTE-R for Indian Railways” (May 2018) by IIT Madras, IIT

Hyderabad & Centre of Excellence in Wireless Technology, IIT Madras

(CEWiT)

4. “Study of LTE for Indian Railways Requirements” – Project Report on “LTE-R

for Indian Railways” (May 2019) by IIT Madras, IIT Hyderabad & Centre of

Excellence in Wireless Technology, IIT Madras (CEWiT)

5. “Adaptation of LTE for Indian Railway” – Project Report on “LTE-R for Indian

Railways” (May 2019) by IIT Madras, IIT Hyderabad & Centre of Excellence in

Wireless Technology, IIT Madras (CEWiT)

6. Technical literature from IRISET

7. https://www.3gpp.org/

8. 3GPP TS 22.179 version 15.2.0 Release 15 - Mission Critical Push to Talk

(MCPTT) over LTE

9. 3GPP TS 22.282 version 14.3.0 Release 14 - Mission Critical Data over LTE

10. 3GPP TS 22.281 version 14.3.0 Release 14 - Mission Critical Video over LTE

11. Technical literature from M/s Nokia Enterprises

12. Technical literature from M/s Ericsson India

13. Future Railway Mobile Communication System - User Requirements

Specification by International Union of Railways (UIC)

https://www.3gpp.org/



Issue of correction slips

The correction slips to be issued in future for this report will be numbered as follows:

CAMTECH/S/PROJ/2021-22/SP6/1.0# XX date .......

Where “XX” is the serial number of the concerned correction slip (starting from 01

onwards).

CORRECTION SLIPS ISSUED

Sr. No. of

Correction

Slip

Date of issue Page no. and Item

No. modified

Remarks



CAMTECH Publications

CAMTECH is continuing its efforts in the documentation and up-gradation of information on

maintenance practices of Signalling & Telecom assets. Over the years a large number of

publications on Signalling & Telecom subjects have been prepared in the form of handbooks,

pocket books, pamphlets and video films. These publications have been uploaded on the

internet as well as Railnet.

For downloading these publications

On Internet:

Visit www.rdso.indianrailways.gov.in

Go to Directorates → CAMTECH Gwalior → Other Important links → Publications for

download - S&T Engineering

or click on link

https://rdso.indianrailways.gov.in/view_section.jsp?lang=0&id=0,2,17,6313,6321,6326

On Railnet:

Visit RDSO website at 10.100.2.19

Go to Directorates → CAMTECH → Publications → S&T Engineering

Or click on the link

http://10.100.2.19/camtech/Publications/CAMTECH%20Publications%20Online/SntPub.htm

A limited number of publications in hard copy are also available in CAMTECH library which

can be issued by deputing staff with official letter from controlling officer. The letter should be

addressed to Director (S&T), CAMTECH, Gwalior.

For any further information regarding publications please contact:

Director (S&T) – 0751-2470185 (O)(BSNL)

SSE/Tele - 9755549287 (CUG)

Or

Email at [email protected]

Or

FAX to 0751-2470841 (BSNL)

Or

Write at

Director (S&T)

Indian Railways Centre for Advanced Maintenance Technology,

In front of Hotel Adityaz, Airport Road, Maharajpur,

Gwalior (M.P.) 474005

http://www.rdso.indianrailways.gov.in/

https://rdso.indianrailways.gov.in/view_section.jsp?lang=0&id=0,2,17,6313,6321,6326

http://10.100.2.19/camtech/Publications/CAMTECH%20Publications%20Online/SntPub.htm




Quality Policy

“We at RDSO Lucknow are committed to maintain and update transparent

standards of services to develop safe, modern and cost effective railway

technology complying with statutory and regulatory requirements, through

excellence in research, designs and standards by setting quality objectives,

commitment to satisfy applicable requirements and continual

improvements of the quality management system to cater to growing needs,

demand and expectations of passenger and freight traffic on the railways

through periodic review of quality management systems to achieve

continual improvement and customer appreciation. It is communicated and

applied within the organization and making it available to all the relevant

interested parties”.



Our Objective

To upgrade Maintenance Technologies and Methodologies and achieve

improvement in Productivity and Performance of all Railway assets and

manpower which inter-alia would cover Reliability, Availability and

Utilisation.

If you have any suggestion & any specific comments, please write to us:

Contact person : Director (Signal & Telecommunication)

Postal Address : Centre for Advanced Maintenance Technology,

Opposite Hotel Adityaz, Near DD Nagar,

Maharajpur, Gwalior (M.P.) Pin Code – 474 005

Phone : 0751 - 2470185

Fax : 0751 – 2470841

Email : [email protected]




INDIAN RAILWAYS

Centre for Advanced Maintenance Technology

Maharajpur, Gwalior (M.P.) – 474 005

LTE Network & its applications in Indian Railways

Documents

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